Oh, my gosh!!
Recipes are priceless!
My favorites are the ones written in personal handwriting.
It makes me think about all the times those recipes were referred to and used over the years.
I have quite a bit of experience with dementia and alzheimer's patients. They often have problems with short term memory, but somethings can trigger them to remember things from the past.
I would try visiting your grandmother if she's in close proximity or even talking with her on the phone and ask her about some of her recipes. You might be surprised what she's able to tell you.
My father in law had dementia and alzheimers. He rarely spoke. I just talked to him as though he understood me. One night, a commercial came on TV with the image of the Statue of Liberty and I said that I wanted so badly to get to see her in person one day.
He began telling me all about how he had seen her when he was on a lay over in New York before being flown to Europe for the war. He told me about a diner he and some of the other G.I.'s had visited and had a wonderful meal. The flood gates just opened and he shared so many memories. He couldn't remember day to day if he had his teeth in or not, but when it came to memories from long ago, he could vividly express them.
Before it's too late, try to enlist your grandmother to help you with the recipes. It might be good for her to try to remember and make some wonderful memories for you too.
I have no idea why your aunt would just throw the recipes away, but what's done is done. Grandma might be able to help you retrieve some of them.
Best wishes.