I always thought she lost her virginity at the night of the senior prom, but now that I think about it I probably just read that in a fic and got stuck with that.
Thanks everyone!

Julie

Mulder: Imagine if you could come back and take out five people who had caused you to suffer. Who would they be?
Scully: I only get five?
Mulder: I remembered your birthday this year, didn't I, Scully?

(The X-Files)