Hello, As described you that she has pain while climbing steps and sitting down the joint space in the knee must have decreased. Please visit a physiotherapist who can give modalities to reduce pain and show exercises to strengthen the muscles around the knees . Ask her to not sit down or not even low sitting .cross leg should be avoided . She can wear a knee cap to give support to the knee and reduce the pain while walking . Please dont start physio at the earliest to avoid surgery.