J.R.
Hi. it is hard to give such advice to someone i don't know but I will do my best: I don't know from your post the age nor if she is on antibiotics, but if she is old enuf to say she is seeing double...I would, not in a panic....call my best friend/sister/mom first to double check my perspective (and someone who knows you and your daughter0, and if she/he agrees, I would go to the emergency room....
GO BY YOUR GUT INSTINCT....