My opinion focus on something like body count doesn't or shouldn't matter, you don't need to know her number even if you don't care..

There could be a deeper reason why she lied, There are couple I wish not to include in the number being trauma or deep deep regret or just wish to forget..

Whether or not could be the case, still shes uncomfortable to answer that question, that's not your business at all really; all you need to know shes STD free or doesn't have a child somewhere

If just thats the only lie shes done then it be a stupid petty reason to break up over. im just looking at the bigger picture, if she's been 100% honest in other parts in your relationship then why end a good thing..

Again this all my opinion my thoughts, just guess comes down if it's a deal breaker for you and If you can look past it or not but only you know that answer..

Coming from a female perspective