Rabbit, I wouldn't worry sweetie. Depression is alot different than dementia, and just because she has depression (are you sure?) doesn't mean that YOU are going to end up like her.
So many people nowadays have depression -- and if we all thought we were going to end up with dementia, we'd all jump off a cliff! LOL So please don't worry about it Rabbit. I'm sure YOU will be just fine.
Please take care of yourself Rabbit, and God bless. Hugs, Lee