Thanks for the input, everyone. It's really difficult to get a sense of what's healthy, average, or "fat" for a ball python. Some BPs people post look like slugs basically, they're so thick! And then everyone comments saying how good they look, so it's confusing. Donuts looks so stringy compared to a lot of BPs I see for scale, so I just don't know.
I don't, I never got a scale because I figured I didn't need one. I do track all her feedings but obviously don't know the exact gram weight of each feeder.
Okay, I have only bumped up her prey size recently. If she looks fat, I can give her smaller feeders again. I have been doing a small rat once a week, for just these two weeks.
I think I got worried after seeing some threads on BPs that were tiny, like hatchling sized, because they were being fed undersized prey. Even though they were eating consistently, they didn't seem to be getting the nutrients needed to grow pretty much at all.