Found out my friend (might!) have lied...should I confront her?

I'm not really sure what to do here. Ok, here it goes - Last night I found some information about how my best friend had lost her virginity to her ex-boyfriend about 6 months ago. That information in and of itself doesn't bother me in the slightest, but what bothers me is that she never told me about this. I can see how it is something private and it isn't like she ABSOLUTELY has to tell me. But a little less than a month ago we were talking and I asked her if she had had sex with her ex and she told me she hadn't, and that she had been waiting for me to ask her that. I told her that I assumed if she had slept with him she would have told me, and she said that was true - that if she ever did anything like that with anyone she would tell me. Except she didn't. I'm just feeling very confused. I want to ask her about it, but what if she didn't want me to know about it? It wasn't like I was snooping around, trying to find evidence that she had slept with him. I took her word and didn't think twice about it until last night when I was presented with this new information. The new source might be false. True. I actually have been hoping it was false simply to pacify my nerves. I just want some opinions on the situation. I feel like there is this huge, awkward space between us now and I kind of just want to bring it up in the open and tell her that this is what I heard, and if it's true then that's fine and if it isn't true then that's fine too, because I'll accept her no matter what and I want to know about these things so I can support her and help her any way I can (apparently, according to my source, she thought she was pregnant). But how would I go about doing that? Do you think it would be best to just try and ignore it, try and stay out of "her business"?

It's hard - I'm sure she didn't tell me for her own, separate reasons, but I can't help but feel like she doesn't trust me or she doesn't feel like she can be 100% open with me. And she lied to me about it. We don't lie to each other... I just don't know what to do.