Luckily I am having it early this time. A few years back, I named a character Laura, and she was Laura through the whole first draft. In the second draft I went to change her name to Lucy, and I had to change every single scene she was in. Because Lucy was just not the same person as Laura. She just...wasn't.
I have attempted to name one of my protagonist's dear friends Susan. And...it's wrong. It's wrongety wrong wrong, and I know it's wrong. I write a sentence like, "They left Susan behind." What could possibly be wrong with Susan in this sentence? It is a straightforward sentence. There is no sense of wrongness of description, nothing that doesn't match internally. The only thing that could be wrong is that Susan is not her name.
Maybe she's Laura.
This feels fiddly and psychotic, except that sometimes there are enough problems in the world without forcing yourself to name a character Susan when she'd rather be Jamilla or Zofia or Ginger or Jill.
(Nope, not any of those either. Damn. I will try writing one of the scenes without this character and see what happens.)