Hello.. Well severe pain in the knee joints,considering her age I guess it is osteoarthritis.. Gradual wear and tear of the bones and the synovial fluid is leading to this...about finger joints pain she needs evaluation.. It's better she avoids sitting on the floor with legs folded..try to keep straight as much as possible... Avoid stairs.. Kindly consult an orthopaedician and also get X-ray done of both knees