Going along with what Rose said.. you could always start answering questions with other questions.

"Are you going out somewhere?"
"What does it look like?"
"It looks like you're going out. Where are you going?"
"Why does that matter?"
"Because I want to know where you are."
"I'm standing right here, and I'll be back later."
"But where are you going?"
"Somewhere on planet earth, why do you want to know?"

Etc etc. You really don't need to give her information. Say "I'm heading out, bye!" and then go.

And really now.. she's wanting to control your sex life? If she brings that up again, point out to her that for all she knows you're not a virgin and for all she knows maybe you've had lots of partners who also weren't virgins, and she will never, ever, have a way to know what is true or not so she may as well stop trying.