I don't really understand how you can completely dismiss the modern Snowmen, the Prequel, and the Bells Clara's being distinct, yet claim that there's no evidence that the rest aren't the same woman.
Until we meet Clara's friend or Clara's mother, or have Bells Clara remember her childhood meeting with the Doctor, we can't really link them as the same life. And I highly doubt those narrative elements will ever get revisited.
I think we should also consider the names of the articles related to Clara. Having Clara's mother and Clara's father implies that they're married and the parents of the same Clara. But they're not.