Is 15 months of age too late for me to change the name of a child I am adopting?

Honestly, I would leave the name. I can understand that the new name would be in honor of her mother, but I think it's best if the name is left the way her mother intended it to be. Then again neither I nor any other random person answering this question knows her mother, so it really depends on if you think that's something she would be fine with. Congrats on the adoption! :)