Hi Christopher,
This ex probably knows a deep aspect of you that not many people do. When someone knows us on a genuine level, it’s hard to let that relationship go. Sure, we can cut contact and end it on a surface-y level. But you will always be connected.
Of course, people tend to romanticize it.
Don’t beat yourself up. But maybe tell her “Hey, out of respect for my current relationship, let’s only keep in touch once in a rare moon.”
Best,
Inky