You find out some dude is texting your SO? Update in OP

Been dating 2 years. Never met the guy. Don’t know who it is. Somehow you saw a text pop up on her phone from ‘Joe’ while she’s in the bathroom. You look and there is a long text chain where it’s pretty damn flirty. More him than her, but it’s not like she’s being cold either.

Do you confront her about it? (Which makes it look like you’re looking at her phone)

Let it go as stupid entertainment?

Overreact, accuse her of something, and back her into a corner?

Let it play out while trying to sneak check her phone to see how it plays out? (This seems like a miserable option)

Asking for a friend of course....

UPDATE: couldn’t stand it anymore so brought it up last night. Apparently ‘Joe’ is an ex from several years ago that will get desperately drunk (she thinks) and text her on random occasionas still but that’s where it ends. She responds, but doesn’t see the need to be rude or confrontational about it. Happens a handful of times a year. He lives in another city (where she moved here from) and she has no plans whatsoever to ever see him again. I didn’t agree with even entertaining his text, but she seemed pretty responsive and non confrontational about it. The text were a lot more flirty on his end than hers like already mentioned. Didn’t even bring up me looking through her phone. I did express that I wasn’t that comfortable with it but didn’t make it a bigger deal than it was. Sorry this is sort of anti-climactic for the OT. This does make me want to somehow keep an eye out for a while to verify, but I’m just not that sorta guy.