Provent-A-Mite (PAM) is a very good way to treat the enclosure. Please read the directions carefully, removing the water bowl and not putting the PAM directly on the snake
It sounds like your snake is acting very stressed out and this makes sense if you just got her. It is strongly encouraged to not hold your snake for a good two weeks (except for cage/tub maintenance) to allow for her to settle in and feel secure.
As for feeding, a lot of members on this forum feed roughly 10% of the snake's weight. Do you have a weight on the snake yet? Also, do you know the age of the snake? Young snakes (maybe up to 200g) many times get fed every 5 days and then it is bumped to 7 days. But remember: This is after the 2 week break in period!!!!!
As for switching to live, this is fine but understand that your snake may never go back to F/T again~ so please make sure that raising rodents is what you want to do for the rest of your snake's life!
Let us know how this goes and if you have any further questions!