I totally agree with you on
Yvonne, but I don't think Evanna would have a huge problem.
Nor would the majority of people probably know about Evanna Lynch. And even so, meh. I think Evana or Evanna are pretty.
Evan I think is very masculine and would be cringeworthy on a girl. But I also have strong feelings about that because it's a family name for me going back 8+ generations.