A couple of users have pointed out that Marty can't have seen Clara's name on the tombstone, because she got saved as a result of Marty going back, so before he went back Doc wasn't there to save her life, and she died before he got shot.
Not necessarily.
She was driving through that area on her own because Doc had not come to pick her up at the station, which he would have done if Marty had not come and warned him to stay away from women named Clara. They probably still passed through the area, and the horses still got spooked, but on that timeline Doc was already riding in the wagon and in an even better position to save Clara's life and impress her.
So it wasn't Marty going back that saved her, it was Doc going back. And before HE went back, Clara had noone to either pick her up or save her, so she died tragically and got the ravine named after her.
Another possibility is that she "originally" died the same way at a later date. It may be that people are destined to die in a particular way, only the time can be changed. Think about it: Doc originally got shot by a libyan, then he got saved by Marty's warning, then he went back a century to get shot by Mad Dog, and once again saved by Marty. So time travelers can't change the way people die, only delay it. Which of course means both Doc and George are still destined to be shot by someone...
Not necessarily.
She was driving through that area on her own because Doc had not come to pick her up at the station, which he would have done if Marty had not come and warned him to stay away from women named Clara. They probably still passed through the area, and the horses still got spooked, but on that timeline Doc was already riding in the wagon and in an even better position to save Clara's life and impress her.
So it wasn't Marty going back that saved her, it was Doc going back. And before HE went back, Clara had noone to either pick her up or save her, so she died tragically and got the ravine named after her.
Another possibility is that she "originally" died the same way at a later date. It may be that people are destined to die in a particular way, only the time can be changed. Think about it: Doc originally got shot by a libyan, then he got saved by Marty's warning, then he went back a century to get shot by Mad Dog, and once again saved by Marty. So time travelers can't change the way people die, only delay it. Which of course means both Doc and George are still destined to be shot by someone...