Unfortunately she won't stop talking about him unless she finds something else to take her mind off him! Good luck! 😆
I would be worried if she wasn't attracted to random strangers! I think cute strangers are there all around you to take your mind off your worries and to help you hone your flirting skills! 😆
Again, as long as its harmless, what's the matter? Let her talk about him if it makes her happy .. just go along with it, tease her and have fun! If it annoys you, just shake your head and smile and let it go in through one ear and out the other!
But given she is only 19, I wonder if its a serious crush .. hope she doesn't get hurt!