You wait, God works everything in his timing, maybe the person being with the other person is God preparing them for you. I remember hearing once about a man who saw a butterfly that was struggling it's way out of the cocoon, so he took his knife and cut it. The butterfly died instantly. It needed the struggle to get it's blood pumping that it may have the strength to live and fly. Sometimes we try to "help" God out by opening the oven when the cake is still baking. The only thing that happens is we ruin the cake.
Now then, let's say that the person is not who God intended for you, what will happen? Well maybe you coerce and marry this person, find out you're unequally yoked, but by then you're stuck.
Or, you find out that the person is not who God intended but will allow it. And it turns out that you are unequally yoked, yet God straightens the crooked paths, but before that happens you have many long hard years of struggle.
Or, you find out that the person is who God intended, but not yet, but you take her anyway, and as a result you "spoil the cake" leading to hard long years of struggle until she "matures", which would have happened a lot sooner if you hadn't meddled.
Or! you find out that the person is who God intended, you wait, but you're still unequally yoked or she's not mature enough yet. Then in this case God has blessed you with a wife, and is intending her character flaws to mold you into the image of Christ. By teaching you to love unconditionally.
Or, maybe she is the one, you wait, and everything is happily ever after. You never know, God always surprises me.
But seriously, when God's cooking don't touch the stove.