Ahh, this age-old.
I have friends that are exes. I think if both parties acknowledge why it didn’t want to work and they still communicate, I think that speaks volumes in comparison to messy break-ups where neither party speaks anymore.
It’s simple: If two people wanted to be together, they would be together. There’s always a sense of ease when forming a relationship as you and your boyfriend have.
Who you like in high school is much different than who you like as an adult. If they’ve nver “relapsed” into a relationship in those ten years, you have yourself a keeper. It’s natural to feel a little jealous and I think this girl is genuine in her intend to befriend you and let you know that she is uninterested and committed.
Trust the Universe and those around you.