Best way to get back an "ex"

Long story short.

11/18 text selfie to girl whose husband committed suicide in 6/18. Girl replies "you look like Jude Law"

12/18 We go on many dates. Day 3 f-close

1/18-2/18 we spend nearly every night together for about 40 days. Multiple Orgasms each night, best sex ever. The sex life was off the charts. Some nights she'd literally orgasm 15-20 times.

The girl is still clearly grieving the death of her husband. She hides me from friends. But is open with her family. Girl is very clear she prefers NO LABELS on our communications. Not dating. Not BF/GF. Etc. I'm fine with that.

3/18 we travel to LA for a week.

4/18 For reasons to long to go into, I break up with girl. Some reasons include Gas Lighting, emotional unavailability, lack of support.

Girl still wants to remain "friends". Yet, when meeting for coffee and a business networking event, she flirted, touched, and gave signs of existing sexual attraction. She is afraid I will "leave the friendship".

I wouldn't call myself a beta-orbiter at this point.

We have mutual work careers that allow us to collaborate. We are traveling out of the country together May 2-6.

Clearly, the goal is to F-close this girl again.

Where can I find best info on how to regain an "ex"? Even though she insisted there are no labels (which means I'm not an ex). Example of no labels. Yesterday I put my arm around her. She asked is that romantic or like a friend? I said, "no labels, it just feels good".

Any advice appreciated.