The Bible says:
"Delight yourself in the Lord and he will give you the desires of your heart." Psalm 37:4
"Until now you have not asked for anything in my name. Ask and you will receive, and your joy will be complete." John 16:24
"But seek first his kingdom and his righteousness, and all these things will be given to you as well" Matthew 6:33
I think it is ok to ask God for things. What we need to remember is the differnece between wants and needs and we need to trust that whatever answer God gives is what is best for us. (Sometimes yes, soemtimes no, and sometimes not yet) The key is putting God first in our lives (delighting ourselves in Him) and seeking Him. When we are seeking God first our desires will begin to line up with His and we will trust His answers.
Great bible verses and some wise comments afterward
I think what God is most concerned and bothered about is whether he ultimately comes first in your life, and whether your love for him is foremost and takes priority over everything else. What's important to consider if someone were to have a mate/partner is to ensure that even though marriage and having a partner is a wonderful thing, that it doesn't risk coming before God, where you look to a mate to find fulfillment before or above God.
I think it's fine to confess and share what the desires of your heart are to God, and that you want to be married (and I think most people probably do want to be). But also to pray that you will have the right motives for wanting to get married, and whether they are good, God honouring reasons. God knows what our heart's desires are now anyway - so admitting them to him and being straight and honest about them in your prayer time can only be a good thing! God wants us to be sincere and real with him and values our honesty, even if we still have some way to go in perfect behaviour

, and not just say what we think are the right things, if it's not genuine. Encourage your friend to share their desires with God, but also pray that God's will for their life will come first and foremost, and that he knows what is best, and ask that if they are to marry, that they are wanting it for the right reasons.
Oh, and just to add sharing our "feelings" or our hearts desires, and wanting certain things in our life to be granted or fulfilled are not necessarily mutually exclusive

In fact, usually the opposite.