Originally Posted by Saddlebag
Since you consider this mare a rescue don't make the mistake of molly coddling her. At 20 she has probably seen a lot...
Probably being the operative word here. Look up BSMS's (I think) stories of dealing with an older horse who'd apparently never been ridden. And my own Ellie, despite having been well-trained for riding, at 18 had apparently never been on a trail before, and had to be taught to load in a trailer, cross creeks, and so on.
I think there's a difference between mollycoddling, and gradually & safely exploring the envelope of what your horse can do. Sounds like you're off to a good start with the walking.