Bottom line...you know that honesty, and fidelity, are not hard lines for her. You know that there are circumstances where she will lie to your face, and circumstances where she will engage sexually with other people. Her honestly, and her fidelity, are conditional. Are yours? Do you feel like you want a partner who does not lie, and does not cheat, as long as they're still in the relationship, regardless of circumstances?

And maybe you know the answer: "But, honesty is all I've ever needed from her, and she couldn't give it to me."

Of course, you've built something with her, so it's on you to weigh whether or not you want to give all that's good up or not.

I'll leave you with a final thought. She was perfectly fine never saying a word to her until you sat her down and told her you had to have the truth. She was perfectly happy to not say a word about this stuff for years. Perfectly happy to hide her drug use, and not say a word. That's who she is, and that's the price of admission to be with her. You gotta decide if it's one you can pay.