Echoing Mike and Dollydo: Being aware that your mom's reality has changed (it just coincided with your shift) so that you can better protect yourself is key.
My dad was a pretty good dad. Until he retired. Until he got bored, lonely and isolated. Until he started drinking to the point of blacking out on a regular basis. He changed. Well, maybe he didn't really change, there were flashes of this behavior before, but he's "gone feral" and forgotten or chose to not practice any social skills. He lashes out at people, then wonders why no one has time for him. He tries to "punish" adults by refusing to speak to them (as your mom did) then doesn't understand why we don't come grovelling back to him. My sister and I are in our 40's pushing 50. We don't do "grovel" anymore.
As for my mom, she's improved with age only in that she's developing dementia and isn't always "there" mentally.
Because I am aware of this and accept it as part of who they are *now* (not who they used to be), I am able to keep myself centered (mostly, now and then I slip) and not get sucked into their warped reality. I still have a relationship with them, although it's shaky (is there such a thing as a solid relationship with an alcoholic? I doubt it). I am still emotionally attached to my parents. But I will not allow their reality to dictate mine.
Stay centered on you, your mom will do what she will do. If I had to take a wild guess, my guess is that she doesn't like your "new voice" because your "new voice" is telling her that you can't be controlled and manipulated anymore. People who are used to being able to manipulate another individual don't like it when that individual quits playing the game.
Wishing you peace.