First of all, it is highly irregular for a snake to regurge after 24 hours of keeping it down. Since you were cleaning, I'm going to assume that it is impossible for her to have regurged shortly after you fed her and you just didn't notice until after the cleaning.

That said, here are a couple of notes that may be helpful:

1) Firstly, give her quite a bit of time before you attempt to feed again. A recent feed after regurgitating will possibly cause another. Snakes have powerful stuff in their stomachs to break down whole prey, and they lose quite a bit of it during a regurgitation. It takes a while for them to generate more, and a feeder sitting in a recently regurged stomach can potentially rot.. not good!

2) Make sure our BRB has access to heat. I keep mine cooler than any other snake in my collection in general, but they do need heat. A lack of heat can cause prey to not be digested very fast. Like I said, regurgitating well after the 24 hour mark is quite uncommon because usually the feeder has broken down enough by then.

3) Make sure you are not feeding too often. Feeding too often may also deplete your BRB of the ability to quickly digest food. If you've been feeding every 5 or 7 days, feel free to cut it down to every 10, at least for a little while, and especially for the next two or three feedings.

4) It's quite possible that if you wait 7 or 10 days before the next feed, your snake will be just fine.

As for the size of feeder, keep it small for the next couple of feedings simply because of the recent regurgitation. For the long run however, determining the size you should feed a particular animal is somewhat of an art. With the exception of snakes that have recently regurgitated, plenty of snakes kept in captivity could be bumped up a size without issue, and usually when someone asks the question if their young and growing snake is ready to be bumped up in size, more often than not the answer is 'yes'. For us to give you a good suggestion on feeder size, take a picture next time your snake is swallowing a pinky and post it up here. Saying that she is 'small and young' gives us no perspective on the actual sizes of the feeder in relation to the snake. Additionally, can we assume you are feeding mice and not rats? Pretty big difference without knowing what species of feeder you are using.

As for how fast BRBs grow.. It's slow. I find this is a species that does better when "slow grown". Our pair won't be at a good breeding size until 3 or 4 years old. They are 2 years old now, and the female is putting on a nice growth spurt. The male is a picky eater and only seems to eat every two weeks, and prefers smaller prey.