You’re twenty, so you’ve probably never heard it, but years ago, there was a song called “Hey Nineteen”. It was about a middle aged guy who thought it would be fun to date a hot young college co-ed. As the song goes on, he realizes it was a mistake because they have absolutely nothing in common, and goes back to his friends his own age to commiserate.
I don’t think it’s wise for a variety of reasons and, no offense to you, but I’m wondering why she would think this is a good idea. Other than just being insecure about her age, I don’t know what she hopes to get out of a relationship with somebody who doesn’t have the same experiences (or, at twenty years old, any experiences, for that matter). I don’t see this ending well for either one of you.
And I’m not Catholic, but I have to wonder how you’d handle the fact that she’s almost reached the finish line, as far as child bearing goes. Seems like, as a Catholic, that would complicate your sex life some.
Sorry to be so blunt about it, but I’d rather hurt your feelings for a few minutes than have you make a mistake that will haunt you for years.
Incidentally, when he played for the Phillies, Jim Thome lived down the street from my sister and her husband.