She is quite clearly an expert at cracking open balls! I reckon they know. I had a very secure ball but the lid still came off if it bashed into something. Charlie actually worked out how to get the lid open while he was sitting quietly in a corner in his ball.
I wouldn't use one to be honest. And during cage cleans you can't keep an eye on them - I always used to put Charlie in his pet carrier when I was going to be spending some time doing something to his cage (if it was during the day) and he'd just go to sleep. Newt doesn't do that and clamours to be out so he goes in a play cage (and still clamours to be out! But at least he has something to do in there).
A ball is useful just to transport them safely from one room to another I think - ie you carry it (carefully) with the lid on - because carrying them by hand is not safe either - they can wriggle and jump out of your hands. But if using one they do need absolutely constant supervision and only to be left in it for 10 or 15 minutes at a time or it can get stressful.
Anyway I'm with the bin the ball consensus! A plastic bin would do as a play cage, as souffle said - eg for when doing a cage sort out. For general out of cage time a playpen area is much better - until they're tame enough to say have on the sofa with you. Newt gets lots of sofa time but he's very tame and also quite sensible (never jumps off - although latterly he's been getting braver at thinking about it!)
Very glad you got her back
Just tell her your sorry and you'll get something sorted. If you've got solid floors then a hallway in a house can be a good out of cage area - providing you can block it off at one end and no holes in the wall!