Are you sure she's being fed enough? How old is Lucy...what size? & what size is her prey? how often is she fed?
There is another possibility...I have seen a snake with internal pain that bit himself*...let's hope this is not the issue with Lucy. (*and that didn't end well...)
She's 2 years now, about 4 foot long. I offer her a medium rat every two weeks but she sometimes skips meals. She refused the one before Tuesday's.
I am really hoping she is just in extended feeding mode and nothing is wrong ....