Mom gives me a hard time when I suggest she shower. Any suggestions?

Mom refuses to shower when I suggest it. She thinks washing up is good enough when it's not. She is prone to UTIs and we have spoke with all of her doctors about it. They said showering every 3 days is sufficient. I can't get her in the shower twice a week but maybe once a week. Today she refused to shower. We were planning on visiting my husbands family and she agreed to go with us. I refuse to take her unless she showers. She continue to get dressed and put jewelry on, ignoring me. She says that washing up is good enough. I told her she might as well not even put any jewelry on or get dressed because I'm not taking her. And she said I'll get a cab there. She doesn't even know where she lives and she could not even make it out to the curb to get in a cab. She's on oxygen 100% of the time. She has advanced COPD, heart issues and a mass in her lung that is suspicious for malignancy (she doesn't know this). Unfortunately she is high risk and cannot endure any invasive testing and surgeries. We have already spoken to a palliative care doctor regarding her situation. She can just about walk and when she does can only go four to five feet at anyone before having to sit and rest. We cannot see my in-laws because she is being stubborn. I am at my wits end end. She doesn't even care about how much my husband and I do to help care for her to enable her to stay in her own home. I am living with her and have for the past four years. My husband lives four blocks away and comes four days out of the week to sit with her while I work. We have one lady who comes in on Mondays and my sister comes another day. I just cannot believe how hurtful she is by actually telling me she isn't showering to spite me. She got me so upset crying that I actually told her I hated her. I really don't hate her I love her very much but she is a selfish person. She has been selfish all her life and I have overlooked it. So now my husband and I both cannot go and I think it's so unfair. I work full time and have no social life. If I want to go out, I have to find a sitter. That is hard because I have only two people and they are here taking care of her during the week. I just do not know what to do anymore. I am getting burned out.