I [22 M] caught my girlfriend [23 F] lying. I'm scared that if I confront her, we might end up breaking up

So before me and my girl started, she had this fwb. Eventually the just returned to being friends again and me and her started being in a serious relationship.

During her time with this guy, she would always come to me asking for advice saying she felt like being used, it was empty and all that... So I comforted her and gave her advice.

So yeah months later and we ended up together. She still kept in contact with the friend but she reassured me it was just him being an asshole and she was just being nice.

But since the start of the new year, He began contacting more frequently and one night I had a moment of weakness and browsed her fb messenger while she was at the bathroom. I saw that she had deleted (technically 'archived' but she doesnt know the difference) conversations with him. Most were just simple friendly banter so I decided to just toss it aside. Cause you know.. trust~

They're last messages were sent during Feb 1. Then a week later, he called her while we were having dinner. I became visibly annoyed and I asked her when was the last time they talked.

She told me it was when we last fought, which was in mid Jan.

So basically I caught her lie.

The girl has trust issues, and lies to her mom constantly cause she lives overseas. Sometimes she just lies to avoid confrontation.

So I just decided to just keep it in because it wasnt really "cheating" conversations or flirting. But as the days go by, I began questioning almost all of the things she says.

I feel like Im slowly losing my trust in her.

I wanna talk to her about it. But between me snooping her fb and the countless of fights we've had about that guy, I feel like if I told this it would eventually lead us to break up.

tl;dr: Girl lies to me and I feel like I can't trust her anymore. But at the same time the lie wasnt the big so Im not sure what to do.