Hi @MummyMountain
I'm jumping for joy on your behalf on your decision to go get that massage. I hope you enjoy every minute.
I am extremely surprised that your daughter is sticking to her promise to follow all the instructions and medical advice given to her. From what I know living with someone who has BPD, promises don't usually last too long. In your daughters case though, I hope she really does follow through with this. That will be a great help to you and obviously to her as well.
Being in your situation with anxiety, depressions and being so burnt out you need to now more than ever have those boundaries in place with your daughter. They do tend to get upset over the smallest things. Most of this stuff you can just let go right over your head. You almost have to put up a bit of brick wall within yourself where a lot of what happens you need to let bounce off you. It's not easy to do because you love them and they may think that something is hurting them or causing them discomfort but you know in the real world that's not the case. It's easy to let yourself get pulled into their world but you have to maintain the emotional distance so that you can be the stronger one.
Looking back I remember getting involved in heated arguments and spiraling down to the level of my sibling when some of the worst behaviour was happening. I'm a lot wiser now and don't fall for it. We still have our spats over stupid things but I'm much more at ease with putting my foot down and calling a halt to a conversation or argument that I can see is going nowhere fast.
Something else I found helpful whilst living with someone who has BPD is to set time limits on the interactions you have. For instance, my sibling used to approach me at all hours of the day (through phone calls at work) or night and want to talk about something, usually some nonsense that I had no interest in whatsoever. That wore thin really quickly with me. If they had something valid to say then I would set a time limit of 5-10 minutes for them to bring up the subject and then we would have another 10 minutes to find a solution. Usually my sibling wasn't happy with the outcome and would always go off topic. Even today my sibling will never get straight to the point of what needs to be said which drives me nuts. I could tune out for most of the conversation by the time they said what needed to be said. It's exhausting to say the least. If there is no positive outcome of a conversation for them then you can reschedule a time to go back to what was being discussed and ask them to think about the points they want to bring up and even write down what they want to say so they don't forget. I have put a rule in place at home where my sibling knows not to bother me until I've been in the door for at least half an hour. It gives me the space to do what I have to do and not be bombarded by their problems.
You need to have some breathing space.
Mostly I think it's important for them to have a moment of clear thinking. In your daughters case she can give you a run down of all the bad thoughts she has had that day and you can address them one by one but at a set time that you determine. She won't be worse off if she has to wait and it will in fact help her have a bit more self control.
I am a bit concerned when you mentioned that you manage your stuff by avoiding people. In hindsight let me tell you that this can be a big mistake. I did exactly what you did and nobody outside our family even knew what was going on and what I was going through. If I could go back in time I would have told everyone what was happening. These days there shouldn't be a stigma any more with mental illness but in the back of your mind you think that people won't understand or they won't care. 99% of the time this won't be the case at all and you will find that you aren't the only person who has had to deal with someone who has a mental illness. You will also find that the support for you will be there from others when you need them. Please, please don't do what I did and isolate yourself. It's terribly lonely and so completely wrong to go through it alone. Don't ever be afraid to reach out, even if it's just to talk about things.
Please keep updating and feel free to ask any questions you may have.