That sounds very close. I'm researching this for my boyfriend - he was born in 1962 when his mother (the former Janetta B. Westwell) was in her forties. He remembers having maternal aunts named Florence, Myrtle, and possibly a Mamie. Do any of these names match up with Janette Butler's siblings?
Herbert Ross Westwell's death date also is compatible with the information we've got - my partner says he only met "Grandpa Westwell" once, at a very young age. (He would have been ~4 years old in 1966.)