I think you did right with the ball. Make her give it, praise her her and then give it back. The ball then becomes the reward. We were told with training you should use 5 different types of treats, 5 toys and 5 lifetime rewards (a walk, jumpin up and givin you a kiss, when maybe you don't normally allow that, stuff like that) You don't have to use all, all the time, but that way you aren't always giving treats, and the reward is always a surprise.

I would start refreshing Jo a little on commands. Call her to you a few times a day. For the first few days when she looks at you, call her over and praise her for coming. Sometimes giver her a reward, other times don't. After a day or two wait til she is involved in something else...playing, eating whatever. Then call her to you. It should help make her comes more reliable. If this doesn't help maybe an obdience class? Even if she has had one, a refresher would help her and remind you to work with her. I have found if I don't do a few commands with my dogs each day they get very lax!
(esp. with Comes!)

Jo, you listen to your mommie. She just doesn't want you to get hurt!