Therapist advised to apologise....

[highlyunreasonable]

DP got a message out of the blue on Facebook from another woman, someone he's no longer friends with on there and certainly nobody he's ever mentioned to me. We've been together 3 years
Message says something along the lines of 'hello stranger, I know this is out of the blue but I wanted to thank you for being such a wonderful friend 4 years ago. Stuart (her partner) knows everything and we've sorted everything out but my therapist has advised I contact everyone affected when I was being a nightmare friend to say sorry.
I'm happy now and hope you are too'

He hasn't tried to hide the message from me but when I asked him who she was it went from 'just someone he used to work with' to (when pushed) someone he had quite a flirty relationship with and ended up meeting up with and kissing (?) despite the fact she was in a relationship at the time.

All happened before we met but my spidey senses are tingling....
He thinks she's just being nice but do therapists really suggest this bullshit? Sounds very self indulgent and a bit desperate attention seeker??

I think you need to say that to him. Explain you are feeling odd about this, and you don’t know why. Tell him you totally trust him, but you can’t shake this uneasy feeling. Be open and honest, see what he says.

It’s better than wondering if she is messaging him and watching suspiciously every time he looks at his phone.

He probably reacted different because he feels Uneasy about what happened between them. But talk it through.

@Dollymixture22 thank you, yes I think you're right that's probably what I need to do. I'll bring it up tonight when he's home from work