That is an interesting assignment. Is the school affiliated with the site?
Anyway, specializing is generally done once you graduate, so no additional expenses. I'm also not quite sure what you mean by "general RN".
I would go up higher in the chain of command as well as give a dated, signed copy to HR. Leave a message on her phone and email her a copy with explanation that it's not ideal, but it's the best you can do.
I am a newbie to health care, so take this advice in that vein.