You let her push your buttons Irish - gotta get a little tougher. You took the bait. Don't do it next time.
Her text was a sad and very obvious attempt to make herself feel better. If her life was really so good, trust me, she would not have been texting you on her birthday.
If you want to be compassionate, just validate and move on. Something like:
"I'm sorry you feel that way about our relationship, I did love you and regret that somehow you couldn't feel it. I'm glad you are happy now. Be well."
I know you're mad at her for her behavior with the girls but I would take that text as further proof that she's really unwell and leave it at that.
