Paranoia can sometimes be a good thing and kudos to you for noticing the difference in your goat.
Could be one of several things going on… like Joe mentioned, maybe she needs a little bit of goat grain now. Or it could be time to deworm her.
Also, dairy goats go through awkward growing phases as they mature. There is super cute kid phase… rolly polly and happy.
Then there is gangly “teenage“ stage, then there is young lady stage and then there is mature doe stage. In the teenage stage they can be a bit rolly polly while still being gangly, but as they start hitting more mature stages and the rumen is developing more which changes the body shape and they’ll start to look more “dairy” like.
The barrel area will look bigger, but the hip bone area will look more “hippy” and pronounced. This is in general… some goats are slimmer, some goats are pork chops ( I mean not mine though…. Mine don’t get over fed at all… *innocent blush*
If your girl has Nubian in her it could be the “dairy“ coming out.
I realize yours is a mix, but sometimes the traits of mixed kids can develop more over time-
Younger doe who hasn’t hit the gangly stage yet-
More mature does and the hippy-ness of the black doe is not uncommon-
More than likely she probably just needs to be dewormed though.
I’d be happy to send you some links to goat websites where you can read more about what dewormers to use in different areas because of resistance issues, or you could call your local vet and ask what works in your area.
Course, you know... now that you have brought her up you have to post a pic...