's advice might make sense if she hadn't cheated before. And believe me, she did cheat. Sexting someone other than your s is cheating. A PA is not the only way to cheat.
Furthermore, you've said she admitted to sexting for the ego kibbles and non-marital, male attention. That is a HUGE red flag. People who are externally motivated - who get their sense of self worth from the attention of others - and go outside marriage for it - and BROKEN people. YOU can't fix that - only they can through IC, very difficult self examination, a level of self awareness most people like this lack, and a miracle change of character, personality and self respect.
So, since we know the true back story (or enough of it) we also have a very good idea what the few outcomes are likely to be. It's human nature and people tend to follow patterns - patterns you can read about on TAM for story after story.
"Spying" in this context is not bad at all; w had proven to have weak boundaries, and you have a right to enforce your own boundaries NOT to be cuckolded.
If she has low self esteem, there is a possibility she's taking selfies and comparing them to girls she sees on the internet to see how she looks. I'll concede there's maybe an 8-12% chance that could be true. Unfortunately, IMO, that means there's an 88-92% it's something very "not good" and frankly I wouldn't need to know what type of bad it is.
So I would put VAR's out, keep the camera rolling, and prime the pump. I'd bring a tripod and video camera into the bedroom and say I think it might be sexy to record ourselves... if it turns out horrible we can delete it together. See what she says. Ask if she's taken any sexy photos already that she can share. See what happens.
If you shake he up she'll go underground but she'll also likely discuss it with her AP if there is one. And that you can catch on the VAR.
It's up to you about confronting - but recognize that being married to someone who seeks attention for self validation is a HUGE risk for infidelity as time goes by. Anytime she doesn't feel she's getting sufficient attention, she's likely to wander. Not my kind of woman TBH
Sent from my iPhone using Tapatalk