Needing advice on aging parent

First thing is, right now I am not in a position for any legal routes to pursue...so I'm not asking about getting POA or anything like that.

My mother who is 70 has been on a decline for many years. She is still married and resides with my father, they are around the same age.
I would like to blame retirement and depression but she started having cognitive difficulties even before she retired.
Her symptoms first presented with chronic sleep issues...they just never got better. Short term memory problems and agitation followed. Misplacing items has become a huge problem. Again, very poor sleep.
Now she's repeating things she's told me more than a few times. Asking me where certain places are she is familiar with(like navigating in the car) and not physically keeping up her appearance.
I am sure there is long term depression underneath that has not been treated properly, mostly due to her unwillingness to address it.
But she seems different, and i have a feeling there's more going on.
I cannot get her to help herself and feel maybe she doesn't have that capacity to do so.
I do worry about her driving, safety reasons.
It's obviously something I've worried over for years but I'm not sure what I can do to help. I do listen and have more patience but I'm very concerned for her mental well-being.
My father is useless. I have one sibling I cut out of my life because of abuse. The only other family she has is her sister whom she rarely sees and she barely does anything social anymore.
She does have tinnitus, arthritis, extreme brain fog,..so these all make it more difficult to communicate with others like she used to. I get that.

I'd just like to help any way I can without pushing her away but wanting to speak up because it's hard to see her suffer and seemed confused a lot.

I'm not sure how to help. She's a shell of a human being.

Do I take a chance and talk to my aunt, whom I'm not frequent with, call my cut off sibling and voice my concerns...that could end badly for me and not sure he would even help.

I need some advice. Thanks