Your friend is obviously not uneducated when it comes to science and medicine, but when it comes to names and history she is. Some people don't seem to get the concept of a proper name, and using an affectionate diminutive for everyday. This diminutive, eg 'Dottie' can be swapped around to suit, or even dropped when the child grows up. For instance if her real name was Dorothea, she could become 'Thea' as she gets older. Possibly remaining '' Dottie ' within the family. People have been doing that for hundreds of years.
I just don't think her daughter will thank her for being a' Dottie 'when she is a teenager. Sounds a bit silly. I swear these days people think they are naming a puppy or a cuddly toy, not a human being. Like' Teddy ', which is now so popular, urrgh!