Clara Clayton

I just came from rewatching Back to the Future 3 and now I'm a little confused.

In the original timeline (before Marty and Doc interfere), Clara Clayton is a schoolteacher who dies in 1885 when her horse gets spooked by a snake, causing her to fall into Clayton Ravine, which is named after her. Since she dies before meeting Doc, that means that Doc never meets her and falls in love with her, but his gravestone in 1955 says "Erected in eternal memory by his beloved Clara". And Doc’s gravestone in 1955 would no longer make sense because it references a timeline where Clara died before meeting him.

Unless Doc somehow was in the same place at the same time as Clara before Marty came to 1885 was and saved her from falling to her death. But at the same time, why was the place still called Clayton Ravine if Clara never died there?

My confusion arises because the gravestone in 1955 mentions Clara, which shouldn’t be possible if she died before meeting Doc in the original timeline.

Or did I miss something?