I have never heard of bumblefoot causing a chicken to stop moving completely like that, usually they will limp because of the discomfort. If you haven't checked her feet in a while then it could just be that she has been suffering from it for a while, but that it is not the actual cause of her problems, just a secondary thing. Had you noticed her limping or looking in discomfort before she stopped moving completely?
A sudden paralysis could be due to a number of factors. Have you checked out the Marek's article by Nambroth? You can find it here:
https://www.backyardchickens.com/a/the-great-big-giant-mareks-disease-faq
It is one of the most comprehensive and easy to understand articles that I have seen about the disease, and includes a section about diseases that resemble Marek's.
Although I don't have any direct experience of the disease in my own flock (touch wood), I have a few more questions which might give others on BYC an idea on how to help you:
How old is your girl, and do you know what breed she is?
When and where did you get her, and do you know if she was vaccinated for Marek's?
Does she have any other symptoms at all (changes to her eyes for example)?
Are any of your other hens behaving differently in any way at all?
Have there been any changes (no matter how small) in their environment recently?
The more information you can give us, even if to you it seems totally irrelevant to the situation, the better we can help you.