So it's stuck in the scales with no wriggle room whatsoever and it'll pull scales off if you pull too hard? I can't think of a pair of scissors or cutters thin enough that could cut through those rings if they're so tight, so yes, oil the leg if that would make it at all possible to slide the ring upwards using just olive oil or butter or so.
Are you doing it by yourself or do you have someone to help holding her? I find the rings quite tricky to remove without pinching the leg even if there's enough space if I have to hold the bird myself as well. You might just need to wait until the scaly leg improves
I'm treating one of mine, don't know how long it will take before it gets better.