Don’t trust my mom

My mom used to talk with my sister about my dad in bed. I wasn’t there with them, I didn’t want to be a part of it.
I was not close to my mom for the past 40+years. In the past 2-3 years, I’ve become closer to my mom and thought she has been super supportive/helpful.
We were taking a picture of something to send to my sister on her phone and I saw she has been communicating to my sister about me.
It doesn’t feel good.

C: Read words from mom to sister on mom’s cell phone
T: She isn’t supportive of me
F: Hurt
A: Don’t interact with mom rest of day
R: I’m not being supportive of me/her?

I’m not sure where more to go with this.