It is side effects from the long term use of steroids.You will have to see if there is another alternative to them you are so lucky they have not affected her before this..
Her poor old body can not tolerate them anymore she is after all 84dog years old.
Because you have not said why she is on them we have no idea if there is other treatment out there.
I would guess you have taken her back to the vet please let us know how you go with wonderful lady.
What is she on steroids for?