It sounds like she is perfectly fine. I know a lot of breeders who feed their baby snakes huge meals every four or five days to have them up to weight for breeding the year after they're born/hatched. If you try to compare your snake's weight with theirs it will make yours look like a runt. If you aren't interested in breeding her I wouldn't worry about her weight too much, especially while she's this young. If you feed her every five days and don't breed her she'll just end up overly obese.