Rosy boa can't keep food down?

My rosy Sophie has puked up the last two mice I gave her. I try to keep her terrarium at the right temps, with the hot side about 90-ish and the cool side slightly warmer than room temp. I have a cheap setup with the heat lamp sitting on the mesh wire of the terrarium lid, and occasionally I use a heating pad I purchased from Walgreens for extra heat on cold nights. She tends to want to stay on the cool side, so I don't think she's absorbing enough heat to digest her mouse. But maybe it's not a heating issue and it's something else entirely. Any advice?

More details about the set-up would be helpful - terrarium size, heat lamp wattage, type of heating pad, how you are measuring temps, etc. Also, how big is the rosy, what prey size did you give, live or f/t, how much time between feedings, how soon after eating did she regurgitate?
IMO, the 3 most common factors for regurgitation are temperature, prey size, and internal parasites.

She's in a 10 gallon terrarium right now. She's not quite big enough yet to where I have to start worrying about upgrading to a 20 gallon (she's about 1 and 3/4 feet long). Not sure of the heat lamp wattage, but it's a ceramic heat bulb. Like I said before, heating pad isn't one made for reptile terrariums, those get too hot, so my herp professor recommended an electric heat pad from Walgreens (normally used for aches and pains) where I can control the temperature.
I give her fuzzies, because they're as big around as the thickest part of her body and she hasn't had trouble digesting them before. I feed her once a week. She usually regurgitates a couple days after eating.

I haven't paid any attention to ceramic heat emitters since the mid-late 90s...at that time, the lowest available was 60w, which is still too much for a 10 gal tank, IMO. I'd recommend getting a digital indoor/outdoor thermometer and getting some accurate temperature readings. If you find that the temps are too high, you can pick up a decent rheostat controller for $15-20 (cheaper, if you can DIY).
You neglected to say how much time you allowed after her first regurge before feeding again. Since she has now regurgitated on two successive feedings, make sure you give her at least a good 10-14 days before offering food again....and make her next meal a bit smaller (not that she can't handle that size, but you need to break the regurge cycle). A bit of probiotic powder (ie Nutribac) is probably a good idea, too.

I've never owned a Rainbow Boa, but from what I pick up here and there on line, seems people keep them a tad cooler then that. Not to say 90 is blistering hot IMO, but some seem to think that it's bordering on their limit.

Have you tried different ranges lower then what you mention above? And take Harald's advice, get a rheostat or something that allows you control over just how hot the heat supply is.

Aside from temps maybe playing a role, now that you've had a couple regurges, you need to let the snake sit for a week, two would be better, before trying to feed it again. Give it time to reestablish the enzymes and gut microbes that do the job of digestion. Else you risk a continuation of the regurgitation's.