I've only seen this mentioned once but I want to mention it again although some people might disagree;
I think she didn't expect things to get this far.
She loved the attention her rotting legs were getting and when the skingraft started to heal, I think she overestimated her body and the medical industry.
She started picking again but wasn't as succesful this time, and now they cut her legs off.
I think she expected another skingraft, which would also heal, and then she would do it all over again. In her mind, there would be no long term issues while also milking your dying legs time and time again for attention.
When the surgery was done, she seemed genuinly unsettled that her legs were gone.