This topic is a more complicated issue that has to go back to topics like free-will, an all knowing God, the concept of eternity/infinite time.
The following is based on commonly accepted truths about scriptures, but unfortunately I can't remember any of the scriptures to quote...so don't trust me unless it's really there.
God knows everything, past, present, and future. God exists in eternity...or put in another way, God exists outside of time. So yes, God knows who you will marry, no question there. We also know that we are given free will...whatever we choose to do, we can. The common argument is "How can one have free will, if every action of that person's life is already known by God...or you are already destined to lead a certain life". I think the answer to that is - Because you do not know what choices you are going to make, you still have the free will to make them. A common example is Judas. He was destined to betray Jesus, but he did not know he was destined to do this, and he chose the action.
So...I would think knowing these things, the answer to your question would be: God knows who you are going to pick for a husband/wife, but when you pick this person it will be your choice. All the choices you made, regarding listening to God's will, prior to your marriage choice, will determine if you end up making a choice that is pleasing or displeasing to God.