can i save my diabetic mom's vision??

hello, my dear community~

i post here a lot, but this time it's not for me, this is me trying to save my mother...

my mom is a long time diabetic with daily average blood Sugar readings of nearly 290 (bad, i know...) and A1C of, i think, 9, much worse RECENTLY because she wants to eat only POTATO CHIPS... i think other people have healed from worse than this, but... she is very uncooperative, doesn't want to try methods or take pills and struggles with me...
but now her vision has started to rapidly deteriorate :(

...i've got her on rain-tree pancreas support formula (2 capsules at bedtime, 1 in the morning) for a few weeks now, plus bitter melon 500mg capsules (1 at bedtime), twinlab MEGA twin epa & dha capsules and nordic naturals cod live oil (1 each at bedtime), to help with her vision... she won't give up carbohydrates but i'm trying to get her to at least reduce carbs to at one meal a day instead of 3...

would you all share your experiences and recommendations with me on things i could get her to take to bring down her blood Sugar ...and especially, is there anything that can help her eyes ...now that damage may have already been done?