what/how often is best to feed her?
-Get her on a regular feeding schedule. Once a week is perfect.

have some small adult mice, would those be too big for her at this size?
-I would get her on rats. they tend to be more fatty and are better suited for BP's. I have a 100gram female pastel BP who is eating Rat "Pups" or "Crawlers" (same thing different names). You'd be surprised what they can eat. Typical rule of thumb is to feed something to her about the size of her thickest body section.

we checked her over and she looks healthy, but she lived in a less than ideal environment.
-Get her in an ideal environment with proper heating and humidity and hides. Then leave her be for a good 4 days or so to settle in. I wouldnt handle or feed her at this time. Just let her get accustomed to her new surroundings.

what should we be looking out for health-wise?
-start her off on paper towels. look in periodically for little black specs (mites). Also, check to see if you see any discharge from her nose or if you hear any wheezing, those are tell tale signs of a Respiratory Infection and needs to be taken care of at a vet asap.