If they aren't growing they won't shed. Most pet store snakes are underfed. She doesn't look too bad though. I wouldn't resort to an assist feed just yet.
It would be best to try different types of prey before an assist feed. What is she eating right now? You could try a size bigger or smaller (something as wide around as she is at ehr widest would be best). If she's on mice you could switch to rats, or visa versa. If she's on f/t try live. Also, if you are feeding f/t make sure the prey is nice and warm before you offer it to her. Sometimes temp makes all the difference.
She's a lovely snake, so congratulations! Hope she starts eating for you.
Currently trying to feed her f/t mice which is what petsmart said she was eating. I think I'm going to try rats though. My other two bp's are on rats.