While cheating can be used as a drug, that doesn't mean it shouldn't be addressed.
Regardless of the cause, someone who will cheat on a partner is unlikely to change. It can happen, but the odds are against it. Someone cheats because of something inside of them, not because of any "lack" or "failing" on the partner's fault.
You deserve to protect yourself. You may decide to get STD testing to ensure you have not acquired a sexually-transmitted disease (STD.) You get to decide what you can live with and what is acceptable. You get to identify and communicate your own boundaries and you get to decide what the consequences will be should they be crossed.
Respect and protect yourself. Set your limits. If she wishes to get to be a part of your life, she'll abide by them. If not, you'll know where you stand and you get to decide what to do then. Also, you can always change your mind.
A respectful spouse does not disappear from their spouse's life with no notice because they wouldn't want the person they care about to worry. I'd never tolerate this in my life, nor would I ever think of doing this to my hubby, no matter how bad my symptoms were.