My heart goes out to your friend, who is so desperately sad. I take it that a substantial part of her sadness is due to the fact the she is single, and wants so much to be married.
I would begin by asking whether or not this young woman has trusted in Christ for her salvation. Either way, this would surely be important to know.
Her question – “Why has God put her on earth?” – is perhaps best summarized in the first point of the Westminster Shorter Catechism.
(1 Corinthians 10:31. Whether therefore ye eat, or drink, or whatsoever ye do, do all to the glory of God. Romans 11:36. For of him, and through him, and to him, are all things: to whom be glory for ever. Amen.
Psalm 73:24-26. Thou shalt guide me with thy counsel, and afterward receive me to glory. Whom have I in heaven but thee? and there is none upon earth that I desire beside thee. My flesh and my heart faileth: but God is the strength of my heart, and my portion for ever.
John 17:22, 24. And the glory which thou gavest me I have given them; that they may be one, even as we are one... Father, I will that they also, whom thou hast given me, be with me where I am; that they may behold my glory, which thou hast given me: for thou lovedst me before the foundation of the world.)
God has made it very clear that He will not share His glory with anyone or anything else. Thus, our highest goal is to seek after and to serve God. Anything we love and seek more than Him is an idol.
6 “I, the Lord, officially commission you; I take hold of your hand. I protect you and make you a covenant mediator for people, and a light to the nations, 7 to open blind eyes, to release prisoners from dungeons, those who live in darkness from prisons. 8 I am the Lord! That is my name! I will not share my glory with anyone else, or the praise due me with idols (Isaiah 42:6-8, NET).
And so my question to this young woman would be, “If your happiness is dependent upon finding a husband, does this not suggest that God is not first in your life, and that if you did find a husband he would take priority over your relationship with God?” If this is so, then a husband is your idol, and God is not your first love.
Let me turn your attention to a text in the New Testament, where Paul encourages believers to remain single so that they might serve God more fully and without the distraction of marriage:
29 And I say this, brothers and sisters: The time is short. So then those who have wives should be as those who have none, 30 those with tears like those not weeping, those who rejoice like those not rejoicing, those who buy like those without possessions, 31 those who use the world as though they were not using it to the full. For the present shape of this world is passing away. 32 And I want you to be free from concern. An unmarried man is concerned about the things of the Lord, how to please the Lord. 33 But a married man is concerned about the things of the world, how to please his wife, 34 and he is divided. An unmarried woman or a virgin is concerned about the things of the Lord, to be holy both in body and spirit. But a married woman is concerned about the things of the world, how to please her husband. 35 I am saying this for your benefit, not to place a limitation on you, but so that without distraction you may give notable and constant service to the Lord (1 Corinthians 7:29-35, NET).
The point I am trying to make from Scripture is that if our relationship with God (through Jesus) is the most important thing in our lives, then we will find joy in whatever circumstance enables us to serve Him most fully. If this is remaining single, then this should be our joy. If this is marriage, then this will be our joy. But wanting marriage first and foremost, and being angry with (or disappointed in) God for not giving us what we want is not what the Christian life is about.
Our relationship with God must be first in priority, over all else. Indeed, God may very well not give us what we desire unless and until He is our priority:
33 But above all pursue his kingdom and righteousness, and all these things will be given to you as well (Matthew 6:33).
We must be content with the circumstances in which God has placed us:
17 Nevertheless, as the Lord has assigned to each one, as God has called each person, so must he live. I give this sort of direction in all the churches. 18 Was anyone called after he had been circumcised? He should not try to undo his circumcision. Was anyone called who is uncircumcised? He should not get circumcised. 19 Circumcision is nothing and uncircumcision is nothing. Instead, keeping God's commandments is what counts. 20 Let each one remain in that situation in life in which he was called. 21 Were you called as a slave? Do not worry about it. But if indeed you are able to be free, make the most of the opportunity. 22 For the one who was called in the Lord as a slave is the Lord's freedman. In the same way, the one who was called as a free person is Christ's slave. 23 You were bought with a price. Do not become slaves of men. 24 In whatever situation someone was called, brothers and sisters, let him remain in it with God (1 Corinthians 7:17-24).
Jesus made it clear that He was to come first for any who would be His disciple:
26 “If anyone comes to me and does not hate his own father and mother, and wife and children, and brothers and sisters, and even his own life, he cannot be my disciple. 27 Whoever does not carry his own cross and follow me cannot be my disciple” (Luke 14:26-27).
As Jesus was speaking to His disciples here, we would expect Him to say that they must “hate” (love less than Him) their wives. Thus, we could just as easily say that a woman must “hate” her husband, in relation to Her love for Christ.
Having said all this, there are a couple of wonderfully comforting texts, which point us to Jesus as our source of comfort:
28 Come to me, all you who are weary and burdened, and I will give you rest. 29 Take my yoke on you and learn from me, because I am gentle and humble in heart, and you will find rest for your souls. 30 For my yoke is easy to bear, and my load is not hard to carry” (Matthew 11:28-30, NET).
6 And God will exalt you in due time, if you humble yourselves under his mighty hand 7 by casting all your cares on him because he cares for you (1 Peter 5:6-7, NET).
I would remind this young woman that the first temptation – resulting in the fall of mankind – was when Satan convinced Eve that God had withheld something good from her, and that she should satisfy herself by acting in disobedience to His Word. Beware that Satan is not telling you that God has unkindly withheld a husband from you, and that you must therefore act on your own to find one. If it is “not good” for you to be alone (as per Genesis 2:18ff.), then trust God to provide a husband in His time, and in His way. I will pray that she will do just this.
6 Do not be anxious about anything. Instead, in every situation, through prayer and petition with thanksgiving, tell your requests to God. 7 And the peace of God that surpasses all understanding will guard your hearts and minds in Christ Jesus (Philippians 4:6-7, NET).
11 I am not saying this because I am in need, for I have learned to be content in any circumstance. 12 I have experienced times of need and times of abundance. In any and every circumstance I have learned the secret of contentment, whether I go satisfied or hungry, have plenty or nothing. 13 I am able to do all things through the one who strengthens me (Philippians 4:11-13).
3 Blessed is the God and Father of our Lord Jesus Christ, the Father of mercies and God of all comfort, 4 who comforts us in all our troubles so that we may be able to comfort those experiencing any trouble with the comfort with which we ourselves are comforted by God. 5 For just as the sufferings of Christ overflow toward us, so also our comfort through Christ overflows to you (2 Corinthians 1:3-5).
67 Before I was afflicted I used to stray off, but now I keep your instructions (Psalm 119:67).
71 It was good for me to suffer, so that I might learn your statutes (Psalm 119:71).
75 I know, Lord, that your regulations are just. You disciplined me because of your faithful devotion to me. 76 May your loyal love console me, as you promised your servant. 77 May I experience your compassion, so I might live! For I find delight in your law (Psalm 119:75-77).
I write this as I would to one of my five daughters (all grown and married). I can recall a book that was significant to at least one of them:
“Passion and Purity” by Elisabeth Elliot