Hi all! I've been gone for a while; things have been really busy at home with the kids, spring break, holidays, etc.
Cherry is doing really well overall. She's at a perfect weight, very healthy, was recently spayed (and that went perfectly), is eating very well, is doing well with housetraining, etc.
One problem we've been having, is aggression. We've been trying to hard to make sure she doesn't turn into one of those tiny little monsters. But in the past two weeks, she's gotten terrible. She will steal something she knows she's not supposed to have and run away, and then growl and try to bite if you even approach her. She does this mostly with food/stuff she's not supposed to have (she KNOWS. lol). She sometimes does it when she's in a comfy spot and you come up to her. This morning, she wouldn't even take peanut butter from me!
We've been giving her lots of treats when we walk up to her, so she knows that us walking up to her doesn't mean she's going to get attacked (or whatever she's afraid of??).
I don't know what to do.

My other dog is so not like this. She does try to put Cherry in her place sometimes, and Cherry will back down when Dorrie gets between me and Cherry.
Any advice?
Edited to add: the growling isn't mild warning, it's very, very aggressive, teeth bared, and biting.