I'm not sure how much luck you could have teaching her to stay on the cage. It certainly is possible, but it could take quite a bit of work and it may be more reasonable to compromise your expectations a little. Is it unsafe for her on the floor? Could it be made safe? Also, when she jumps off the cage is she coming towards you or other family members?
If you want there are certainly ways to encourage her to stay on the cage to a degree, but completely... its rather like telling a 6 year old to sit in their desk all day and not leave - you may do a lot of training, offer rewards, and appropriate punishments, but the expectation just may not be realistic.
Anyhow, consider if you really need her to stay there - or maybe if she could have other acceptable perching places but the floor would still be off limits. Then we can come up with the right methods to get her to stick to the rules.