Help me NOT write that text

It’s been almost 8 months since the discard. FA breakup (couples therapist confirmed it). She started dating right away and 3 months afterwards she was in a relationship with someone else. She posted lovey dovey things for Valentine’s Day with this person…

We had been best friends for 8 years, together for 4, living together for 3. She never confronted me in person, never wanted to see me again. The last texts we shared were in October before I found out she was dating someone else.

I will probably have to see her for work in two/three weeks and I have started thinking about her again… I hate that she’s still in my mind, and I have not been able to date again to this day while she’s in another relationship. I am struggling not to reach out with the work excuse to tell her that I know about the new relationship… I know I should not. How can I stop this loop though.