And also...(sorry I couldn't just add it to my previous post, but I am not signed in)...would your opinion change if she wasn't to go by Josephine all the time, but would sometimes go by a nickname like Joey or Posey?
Well since your mom's first name is Kelly and not Jo, then I think you are doubly ok with the name being sufficiently honouring and yet not overshadowing, even if she goes by Joey or Josie or something like that. I still think you are good to go!