My AH's mother is very similar. Sometimes I think she really sees him as a child. She used to call me a lot. I put a stop to it. Now I tell her to contact him.
Her denial of everything that has happened during his addiction has actually caused me to distance myself from her and have very minimal contact with her. And, when I stopped taking her calls, I made the decision to no longer call her when I'm sick with worry about him or angry about something he did. I also stopped calling her to check to see if he was telling me the truth about things (For example: "My mom lent me money for that utility bill" or "The money is missing because my mom needed some extra cash to fix blah-blah").
When I did call her to talk about why things could be the way they are, she usually suggested I was to blame or I wasn't being an "attentive enough" wife.
When I distanced myself, I started to feel better.