Abdomen getting smaller

[ruraltool]

A. Avicularia, 2 or 3 inches. Left a crushed superworm three weeks ago, dead as hell, and it's gone-- had to have been eaten, like usual. For some reason though, the abdomen keeps getting smaller. Normal?
Can pre-molters eat but change physically like this? The abdomen was black but now it's getting brownish hairs where it connects to the rest of the body. Can't get a good picture, sorry. I've been offering a new worm every night but the tarantula won't take them. I usually feed once every 1 or 2 weeks. Her enclosure has a lot of connection points and fake plants on substrate so I don't think she fell and hurt herself? Sorry if dumb I just want to be sure she's ok. When I offer wiggly worms she just walks away, so I leave them on her castle as they die from head-crushing and remove them the next day.

 

[Tenebrarius]

live food is probably better. not that i've had problem with prekill feeding my avic, but more likely is that your spider doesn't want to eat, and if it wont it it just wont eat.
I don't know how serious the abdomen is shrinking so I can't really say much, but it could be premolt, never seen abdomen shrink from premolt, only post molt
if there's no problem with care, just keep it hydrated and wait.

 

[MainMann]

I know you say you can't get a good pict, but it makes things really hard if a pic isn't available. Maybe try using a cricket as prey, most Ts go crazy over crickets. Either than that, make sure there's a waterdish in the enclo and try to feed every week. If the T is in premolt, she'll molt when she's ready.

 

[Vanessa]

Very often people think that their Avicularia are too thin when they aren't. Arboreal species have a different body structure and should never be as chubby as a heavy bodied terrestrial. Unless you can show us a photo, we can't give you advice on whether your tarantula is dangerously underweight.
Many tarantulas need fast moving prey to trigger their feeding response. As much as I have tried, I could only ever get about 25% of my collection to accept super worms on a consistent basis. I had to switch back to crickets, as much as I can't stand them. If you are worried about your tarantula losing weight, and assuming that their enclosure is appropriate since you have not provided photos, the first thing that you should do is offer a faster moving prey that will trigger their feeding response.
You really need to provide photos, please. There could be more going on that nobody is going to be able to help you with, without them.