I know that awful feeling of betrayal. I always feel I betray myself when I gamble. Rejection, frustration, being pushed away or ignored are some of the factors which contribute to our “downfall” i.e. gambling.
I think your mum pushes you over the brink emotionally. When people who are close to me do that I often think “Why bother” but we both know there are lots of reasons why we should bother!
From what I read your mam will never change. I also hear you saying she has gambling problems. We all know what gambling does to our moods and our health. She seems to be using you as her punch ball and scapegoat rolled into one. This is the coping skill she has learned to avoid facing her real problems. She seems angry and full of fear. Time for you to give her a wide berth!