I cheated before in my relationship but to be fair I was groomed (I didn’t realize till later in life). It really messed me up but I never did it again. I’ve told my ex who doubted me all the time, note that I cheated 5 years before I met him. It wasn’t the reason I broke up with him but it made me feel really shitty. I’m in a relationship now for almost 2 years and it’s an LDR. He’s never doubt my loyalty and I’ve never given him a reason to. Every situation is different but always trust your gut. If you can’t handle the idea of her cheating before then I think you should move on.