I need advice on dealing with lashing out and temperament issues.

My Mom is in that grey area where she knows she's not 100% but she doesn't want to admit that there are things she can't do. Her communication skills are deteriorating in that she doesn't remember conversations or she chooses words that mean the opposite of what she wants and then gets mad when you do what she asks.

I'm trying to learn how to respond to her in the best way possible but its damned if you do and damned if you don't. Plus I realize I'm grieving the Mom that I used to have and have times where I just want to shake her and tell her to snap out of it. She gets mad at me if I tell her the truth, but she also gets mad at me for "patronizing" her. She also thinks I lie to her. As a Mom that was her default for us kids; we were always lying or trying to hide something. We couldn't win.

I need some advice on how to speak to her and how not to let myself take it personally.