She’s still in love with an ex from 10 years ago. What should she do?

“I’m still in love with my ex from a decade ago. We’ve hooked up on and off over the years and we’re both single now. I don’t know if it’s right to pursue it again because he broke it off the first time. I don’t want to ruin our friendship, but I can’t help but feel ‘what if’. What would you do?”