Elderly mother with lifelong mental health issues

I have recently joined this forum because I don't know where to turn next, so any suggestions would be helpful. My 88 year old mother has borderline personality disorder and depression, but of course now aging is also having an impact. She definitely does not have dementia, as this has been a lifelong issue. I am the youngest of 4 kids. My 3 siblings cut contact with mum a few years ago & I am now her carer & the only one in the family who will support her. I've done everything I can think of to help her & make sure she's safe, & at her age realise nothing will change - especially since she wont take meds & has no insight into her condition. I've been in contact with her GP, the local aged person's mental health team, & she had an ACAT assessment 2 years ago. However, as long as she is safe & not in danger of harming others, apparently there is no more they can do. ACAT provided approval for short term residential respite, but mum wont go. I have teenagers of my own to care for, including one who thinks she is transgender but is still finding her way in the world & confused about identity at this point. I have no issues with supporting my daughter - my reserves are depleted whenever I need to resolve any issues surrounding mum.

This is all very tiring. I have come to the realisation that I am the one who needs the support to be able to continue coping with the situation & continue as a carer. I wont cut ties like my siblings have, but when I ask them to step in & help they just refuse. I have been looking online for a support group but nothing seems to be relevant to my situation.

So, I would appreciate some helpful tips, or maybe just a chat with anyone out there who can relate to my situation. Thanks!!