Can you cover the pool when you are not using it? It sucks to have one and let it go to waste.
I really swear by swimming. It's such a great workout for both dogs and humans. I think it's why Jackson is in such great shape, he has awesome muscle mass and is really skinny (well, not TOO skinny, but perfect, IMO). I owe most of that to swimming and it's no stress on joints. Or could you get could a nice ramp she could climb out of (in the pool), or a cover, or some sort of small fence to keep her out of it when you are not outside? Believe me, I'm all about pool safety, I run a charity foundation on it. So I understand your concern.
As far as weight loss, up hill works too. I live on a big hill so I try to walk up our LONG driveway a few times a week w/ Jackson, for both of our sakes. Not sure how great that is for the joints but I think it will help with weight loss.
A lot of people swear by glucosamine. Actually, the Zuke's Hip Action treats get a lot of great reviews. Worth looking into and most dogs (even my picky dog) takes them as a treat.
Good luck w/ Callie, let us know how she continues to do.
You can kind of see his 'figure' in these pics.
Hehe, I wish I could use the bath-tub. Both Callie and Jackson are about 16lbs so I'm not sure the bath tub would work. Jackson can walk right across it, LOL.