Since she's 2.5 years out, the pouch test is one thing she can try.
She should also review the
Pouch Rules as not following that is probably one of the reasons she's regained. Ask (or just watch if you have the chance to eat together), if she drinks with her meals or immediately after eating rather than wait an hour, as that will wash the food out of her pouch, which will prevent her from getting the full feeling.
She also needs to get help for her depression, as depression often gets in the way of weight loss.
If she says that she never dumps (which is actually something you should not depend on) and never feels full, and can eat over 6oz in one sitting (without drinking at the same time, or immediately after the meal instead of waiting one hour), then her stoma may actually be larger than it should be, so she may need to get a scope done.
These are some things that come to mind.
So long as her tool is intact, she should be able to lose again, and get to goal, but since it's over two years since her surgery, it is going to take a lot more work than immediately post op, and will need to stick to the eating rules and get in plenty of exercise.