As a breeder of mice for many years, I don't recommend you feeding jumbo mice, ever. They're actually old retired breeders that carry a lot of body fat, & they'll do the same for your snake.

A growing snake needs balanced nutrition, otherwise you end up with a snake that has a larger body (more fat) but small bones (like you're already seeing with her "small head" size.)

You mentioned that your snake is "petite" so she may also regurgitate a jumbo mouse because all that fat is harder for a snake to digest. BE GLAD that she's willing to accept multiple items per meal- some won't- because this will make it easier for you to switch her to rats when she's a little older.

While it's best to feed snakes the most mature rodents of the proper size (more mature rodents have more minerals- bigger bones), there comes a point (old rodents) when that's no long a good idea.

There is also no appreciable evidence that rats are better nutrition for BPs than mice are, especially when you're talking about rat pups- & while some continue to disagree on this, just remember that wild BPs didn't evolve eating either one- not domestic mice & not domestic rats. So if you want to duplicate nature, you'd be feeding ASFs (African soft-furred) but they cost a lot more because they're harder to breed, & not available (or even legal) everywhere. And you'd probably be stuck feeding them forever if you tried them, since BPs often prefer them, apparently.