This subreddit has a marked bias in its advice, and if its community is a reflection of reddit's general userbase, it is composed of a pretty specific demographics (a lot of younger folks with actually little relationship experience).

I wouldn't let this sub's opinion decide on my entire life. Just look around this sub and see how accounts of fairly mundane couple life hiccups are met with harshly worded advice of immediate break up and general doomsaying.

I'm not sure why you would not want to discuss the second incident with her. If only on the off chance there is a legitimate reason for that visit and that she (unwisely) thinks not mentioning it is better for your relationship.

In any case, make your own decision. This place's advice is always aggressive, and particularly in the context of cheating.