Nah, not dirty. She's legal. Just don't expect it to go anywhere. The day you start talking about some important social issue, or a band more than 5 years old, and she says "Who/what's that?", you'll know what I mean.

When I was 35, I dated a smokin hot 19 year old. He was a nice kid, but when it came down to it, he simply didn't have a frame of reference for a lot of the things I was talking about. It wasn't his fault. He just hadn't been born yet LOL!

Screw your ex...she's just hating on you cause she lost out.
And why are you telling your mom about a first date with anyone? I could see if you guys had been seeing each other a little while.