£0 remaining for a orthopaedic mattress

This single lady, who is unemployed and on benefits in a private rented flat, has recently become debt free through Christians Against Poverty. She has no savings to fall back on and is trying to stay out of debt. This lady is being treated for back pains and her GP has suggested she gets an orthopaedic supporting mattress. She has found one in Dunelm for £249 and is requesting £200 towards the cost