Ex sister is my “BFF”

I say “BFF” loosely. She used to be. She’s always been the type to choose her toxic man above everyone but now it’s just gotten to the point where I’ve spoken up about how it makes me feel 2x now but she continues to put me on the back burner but tells me “I understand how you feel but you know the situation I’m in rn” ... mind you she’s been in this same “situation” for 5 years since I’ve known her... I’ve told her I don’t appreciate her dude dictating our friendship when I’ve done more for her than he’s ever done or ever will do. She calls me on her lunch break to complain about her life then it’s bye and then repeat the following day. She doesn’t see me nor can she unless her dude is working because she’s not “allowed” to be friends with me. But I’ve noticed now that she will only attempt to hang out with me on a Saturday while hes at work IF i tell her ima go to the gym. It’s gotten to the point that I don’t even tell her my problems anymore and I just listen to her complain when we talk. It’s become toxic to me and at one point I really thought we’d be friends forever but how can you be friends with someone that forever chooses their toxic partner over you & complains about their life but does literally nothing to change their circumstances? It’s annoying and frustrating and I need to just lose contact with her. Her relationship is toxic af and it’s too much for me to deal with now..