<human>: Can you summarize the given text in a few sentences?

The last time I posted on Reddit about my girlfriend, I was worried about her on some trip with two twats and their promiscuous friends and long story short she cheated on me there.
When I messaged her half way through the vacation week telling her I was uncomfortable, she comforted me about how she's faithful, and then didn't mention she kissed and touched up another girl (something way over both our boundaries, or so I thought). Only now has she come forward, over a month later.
We've been together for three years soon, I loved her and I never thought she'd do this with her family history making her so averse to it.
I constantly let it go when she talks about how hot she finds other people (which is all the time, at least a few times a day) because I never believed she'd act on it, but she is the best thing that ever happened to me
Do I leave her or do I forgive her?
<bot>: My girlfriend cheated on me, but apart from that she's the best person I've ever met, I genuinely though I'd marry her. what do I do?