Any advice for keeping loved one from removing diapers?

Amazon has jumpers that zip and snap from behind and be sure to get the ones with zippers on the legs for change or bathroom visits

Does she have pajama pants on while in bed? I would think that that would make it a bit more challenging for her to remove her diaper.
It does sound like it may be some kind of agitation as well, so please talk to your mothers hospice nurse to get some medication for her agitation.
Good luck.

You could dress her in an anti strip jumpsuit

https://www.silverts.com/adaptive-alzheimer-s-antistrip-suit-for-women

But of course that makes changing her more difficult.