First of all congrats on the new addition!

I would probably make her sleep in the crate for a little bit until you are sure you can trust her to hold her bladder overnight.

As for the fleas I am not sure. Are they alive? If so I'd give her a bath using diluted Dawn dish detergent as it kills fleas and isn't too harmful on the skin. If they are dead you can get a flea comb and comb them off.

Good luck. And thanks for rescuing this little girl.