You have to decide for yourself if the A is a deal breaker for you.
If it isn't stop snooping Right now. Now you know and that all you need.
If it is a deal breaker then you can do whatever feels right to you. If not then you have to decide if telling her will get you closer to your goal of saving your M.
Starsky is very good with this I will let him handle it.
I'm probably the wrong one to ask, as I'm a BIG proponent of the ongoing gathering of good intel to protect your interests.