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No, Grandma's mother and official father were Scottish, a grocer and a farmer's daughter. I have her birth certificate; it gives both their names. But I know they only married a couple of months earlier (I have that certificate too) and I know Grandma does not look very Scottish, and thought she had an Indian father. There is no obvious Indian connection anywhere. None of them, as far as I know, ever went there.
It is quite possible her mother had a relationship with an Indian, all the same. She had three daughters (the other two left no descendants), the first two outside marriage, and seemingly all to different men. You will be relieved to hear she abandoned her giddy ways and found religion in middle age.
I would like to know more, but there is no further evidence anywhere (censuses, street directories, newspapers, family effects), so I suspect I will have to settle for that.