My mom is really getting me down and im having a hard time staying positive.

So i was talking to my sister on the phone today and my mom(who was legit in the room right next to me) texts her saying “i love you more than emma!❤️❤️❤️ so much more!” I don’t know if i got the wording exact (ill put a picture above) but I’m really hurt. I used to see a therapist regularly and she basically told me that i needed to morn the mother that i was deprived of because at this point she wasn’t going to change. My mom has always played these games with my siblings and i to try and turn us against each-other but she kinda stoped last year because my brother called her out for it. Ive been trying really hard to ignore the rude comments she makes at me and the manipulation she uses against me but its been really difficult lately and today really got me down. I honestly have no idea what to do to keep her negativity from affecting me. Any suggestions? Also i wasn’t really sure where to post this so sorry if this is not the place.