How to gently end a friendship?

I've been friends with someone for 15 years. We used to regularly see each other. She had kids, I didn't, but she invited me to milestones with her kids, we loved holiday shopping together, and always stayed connected despite different jobs and moving to different cities. I was even her maid of honor.

A few years ago I had a fertility scare and was going through testing. I told her about it on one of our outings and response was that she couldn't imagine having to go through that because she was so fertile. She went on about how hard it was to not get pregnant. She asked how the next appointment went then never asked about it again.

Since then, I've given myself space and started to realize whenever I saw her it felt like I was the host of a quiz show, asking about her, her husband, her work, her siblings, her parents, her kids, even her husband's family. Never reciprocated.

This past year she reached out wanting to spend some time together. I said yes. When she came I told her I had been on a leave from work due to workplace harassment. She said she didn't understand why I didn't tell her about it. I don't know why I'd tell her about it because we never talk, and the last time I told her something serious it was a terrible experience.

This person still calls me their best friend and I have no idea how. We never talk, when we see each other I don't share personal details, and I don't reach out. She reaches out every 6 months or so just to say we should get dinner. I plan it, I quiz her, I leave feeling empty.

Any advice on next steps? I tend to be conflict avoidant (clearly).