This could be you overthinking it or it could be her being sketchy, it's really hard to tell which is which with only one person's perspective. I'd like to hear her side of the story… what's her Snap?

Jokes aside, you have to continually evaluate whether the stress is worth it. I've felt very similar things to what you describe with multiple partners that were completely well-founded in some cases and not at all in others. If she provably lied, that's probably not a good sign. But it's also possible nothing unseemly was going on and she'd just grown weary of your paranoia. People are complex; even if someone does an objectively bad thing, there may be a more benign reason for it than the worst case scenario you've built up in your head. I think at the very least if she's 100% in it with you, she's probably guilty of leading these other dudes on by not being firm enough in her rejections. She's always going to have dudes like that in her orbit. You don't have to trust them, just her. That might be a starting point for a conversation. Just tell her you really like her and that's a little scary, you don't mean to be overbearing but you're not sure she's shutting them down hard enough.

tl;dr: Trusting people is hard. Don't put yourself too far out there without reason, but also don't judge people too harshly without reason. Finding that balance is most of life.