Why does Medicaid need my bank account balalnce?

OK, so mom's SS check goes to her account, but then what? Are there a lot of cash withdrawals that have no receipts? That can get sticky.
Was she paying you a sum for transport, room and board? Again they will look for detailed records.
Was she paying you "off the books" for her care? They will consider that a gift unless she issued a 1099 or a W-2

If it looks like there is any "comingling" of her income /assets & your income/assets, then Medicaid would need to review both. But other then that, your income /assets should never ever be a factor in your moms eligibility.
Coukd be this caseworker has just made a mistake, I'd firmly say that your understanding is that since only mom is filing for medicaid, that only moms funds need documentation. If the caseworker persists, I'd fax over a short memo to their supervisor as to this & within this one list all the documents already submitted.

If your names are somewhat similar, it could be there is some crossover if they pulled a credit history on mom that has flagged her application that assets are commingled.

My mom has her own account. I don't know why my finances have anything to do with her getting Medicaid as this is for elder care for her. Thank you for your reply.

Do you and your mom have a joint account? Is there some reason they may believe that she has deposited her funds into your account? I'm just trying to figure this out. Maybe some others around here may know the answer to your question. The only think I know is about why they ask for the recipient's bank statements.