I don't want to endanger her benefits, thoughts please?

Hello asking for my sister

She went in to hospital for a routine operation, which went and led to serious complications and errors admitted by the NHS, of 11+ further operations. She was hospitalized for a year, in various hospitals, ending with re-enablement.

Having left hospital she has a care package (which the council want to charge her for) in place (& 3 district nurse visits per day, is disabled).

The authorities are working on a plan for her, physio, occy health etc. I have secured ESA for her, Pip awarded but not in payment yet.

Her SSP was exhausted, the firm have now been bought out under TUPE, but her manager seems to think it would be best for her to resign?

They offer her 12 weeks full pay, I don't want her to endanger her benefits, for resigning any thoughts please? I mean shes not getting paid sick by them, no way of returning as further surgeries due and due to the meningitis she endured, her pathway of thinking is slow processing, she is unable to walk, far, can't stand, has special shoes, fatigue, oesophageal stoma, and a clenched fist and severe dystonia torticollis in the neck.