Ok, that's all very helpful information : ) .
I think you need to think short-term, while you and your sister are living with your grandmother, and then long-term, when it's just you, or you and your sister. I think it might help everyone -- you, your grandmother, and folks here offering suggestions -- if you start thinking of what you're doing now as more of a "refresh" than a remodel. A refresh can be inexpensive and cosmetic, limited to things like new kitchen towels, a new mat in front of the cooktop, and maybe a paint job; I would also look into a gel mat, which your grandmother find more comfortable and easier on her feet and joints. They come in different colors and patterns. Just make sure whatever mat you choose isn't a tripping hazard for her.
How does your grandmother feel about a remodel? Is she excited or nervous or not particularly uninterested or ? If she's not 100 percent thrilled, I'd move very slowly with this. A new mat, kitchen towels, maybe a paint job.
What I would do in preparation for the long-term is use the kitchen a lot. After about a year, you'll have an idea of what works and what doesn't work. Then start thinking about what you would do, and then how you'd pay for it. One side benefit of this approach is that you'll have a chance to spend lots of time in the kitchen with your grandmother, cook with her, learn her recipes, and make some more memories to keep in the future when you're in the remodeled kitchen.
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