I think she's already aware that if you found out how many people she's been with you'll leave her. Which from what you've posted here is a very real possibility, that's why she's asked you so pointedly.

To me body count just doesn't matter at all, you could have slept with 6 or 600 people and it makes no difference (although I'd be curious about the 600 lol)

I think you need to gey your head straight before you have the conversation - if it isn't an "acceptable" number to you what are you going to do? If she genuinely doesn't know what are you going to do?

And then I'd just say, look let's just get an awkward conversation out of the way, how many people have you been with? And go from there.

Anecdotally though, everyone I've met with a low number of sexual partners has had really messy divorces and regretted marrying with so little experience. All my old ho friends (and me!) Are much happier/secure in our relationships. So I just wanted to pitch it's not always black and white :)