toxic mom?

I have always had mental health problems, as well as problems with my mother. she left me and my brothers with my dad without any warning when i was 10. She would come back into my life after months/years and then leave again. her partners were always rude and toxic, until she apologized to me for everything she did last year, and i gave her a second chance. I am currently working and in college and living with her and her partner. i am working on moving out, it’s just stressful when you make minimum wage. so i am saving all i can!! anyways, i have told her 2 times that i need to get back into therapy and that i’m needing some mental help. All she says is “okay we will look into it.” and she never brings it up again. but a month ago my mothers partner told her the same thing and she got up and got them help right away. why isn’t she giving me this energy back? especially being her daughter? people have always said that my mom is selfish and only helps herself and the person she is with but i never wanted to believe it. is it true? what can i do about this? all advice helps! i’m struggling.