I have part been dating my boyfriend for just over 3 months,and he has part started his 3rd nitanati in med school. My seminary teacher went off on me about matchmaking a non Mormon when I was talking about going to his prom.
We all wondered why nitanati would go against such a blessing. While it's true that Mormons are not one-dimensional and completely predictable, the odds of a successful relationship, given the OP's matchmaking of his girlfriend, are slim.
If you can genuinely deconvert her then cool.