A couple of months ago, I (accidentally) stumbled upon some information that someone I know very well (who is married) is being very flirtatious with another man, apparently an old flame (who's also married, and has a family). I've continued snooping (I know it's wrong, but it was very shocking to me, and I just couldn't help it), and she seems dead set on trying to get "involved" with this other guy. He keeps contacting her, but he doesn't seem very receptive about cheating on his wife. He really wants to be friends, though, and continues contact.
Why am I so conflicted? Because the woman in question happens to be my mom. Her and I have been very close since, like, forever. I've never in a million years thought she was unhappy with my dad, or had it in her to pursue an affair. This whole thing is just so bizarre to me.
Their contact has mostly been online, via Facebook. In the last month, they've apparently started texting quite often (though I don't have access to any of their texts, just the computer stuff), and he occasionally calls her, and she makes sure to take the call in the basement so I can't "listen in".
I don't really want to come right out and tell her I know... Aside from the fact that she'd be super mad at me for snooping, she's written some pretty unpleasant things to this guy, and she'd probably be mortified to know I've seen them. I've tried to subtly question who she's talking to on the phone in the basement, and I've hinted around that something just feels wrong about her lately, and I thought I had scared her off the whole thing, but she seems to be back in contact with him.
She defends herself hiding in the basement to take his calls by accusing me of always "eavesdropping" on her phone calls when she talks to me grandma, my sister, etc. Admittedly, I've overheard stuff from her conversations and inquired about them later, but I wasn't specifically eavesdropping; I just happened to be in the next room, and we have a very small house...
I dunno what to do, though. It's really bothering me, but I don't feel comfortable confronting her on this, because I think she could easily derail that and turn the issue around, and start a huge family fight. I don't necessarily want to tell my dad, though, because I don't know how he'd take it... When he lost his job a year ago, he basically had a mental breakdown. I'm afraid the news of his wife trying to cheat on him would severely depress him, and possibly cause him to do harm to himself...