PIP (Personal independence payments) ?
Whether she would qualify after assessment, cannot answer.
Go to Job Centre and book an appointment with a Disability Employment Advisor. Perhaps she can then discuss help available.
Yes, splitting a single card claim into multiple claims would cause problems. If/when the bank looked to settle a claim, they'd want you to agree that the refund is in F&F Sett't of all claims regarding that account.
Secondly, please hold off sending the letter(s) while Site Team discussions are ongoing about this case.