I wish I had more to offer, but reassuring your mom that this is not her fault, is one of the best things I feel you are doing. And try to let your feelings of guilt go, and like you tell your mom, these are things that happen, no one is to blame.
I think support groups are so helpful in so many ways, I attend one every month for dementia/alzheimers support, meeting others who are going through similar stuff with their loved one(s) who are afflicted with a disorder really has helped me emotionally to deal with things a little bit easier as well as educating me to what's to be expected or not what to expect.
The facilitators often have guest speakers in the medical and research fields that help our group with the latest info, which is a great help in coping.
I wish you luck with this, I hope your mom will open up to giving the support avenue a chance.
Maybe both of you can attend one?
Please take care, and feel free to drop by here whenever you wish.