I would say that as long as you have mentioned to the parents that you won't be held responsible for dirty/mangled dresses and tights.... just play on!!
I also have one of those girlie-girls. She would wear "long, long pretty dresses" every day if I let her. And as someone else said; at least they get worn enough times to feel like you get value out of them!
I actually have a section in my handbook that discusses appropriate clothing for daycare, and that I cannot promise they will be clean and shiny at the end of the day. I tell parents to bring extra clothing if they anticipate going somewhere "special" at pick up.
I am with Reggio on footwear, though. If Little Miss was showing up in frou-frou shoes that she couldn't play in, I would be asking parents to ensure that she has PROPER shoes to play in!!