One of the most useful things I learned early in recovery, and a concept that grows deeper and deeper for me as I grow in recovery is the idea of humility. Humility is being honest and living honest. It is about reality, unvarnished. I am neither better or worse than I am. Life is neither better or worse than it is.
I have capabilities. And I don't have to hide them, nor crow about them. I guess what I am saying is that, if I think about it, boundaries are real. There are some real things that I can do, and can't do, and I can lie, varnish, hide, parade all kinds of images and ideas, or I can just be real honest.
If you honestly can't be there for her there it is, a boundary. A REAL boundary. For me, I can't drink, drug or get into flirtaceous relationships. I can't, because I have no sense of control or proportion in those areas and my life goes all to crap when I indulge. That is my real boundary, and I'm not happy with it, and I've tried to fudge, and blur, and cheat, but reality is always the same. Humility suggests that I just be honest. It's so much simpler than trying to dress up the truth.
Humility also means I am honest about what I can do, what I can handle. Because I am just as likely to get all dramatic in the opposite direction and be all woe is me...have myself a pity party, make like my life is over, etc etc. But when I am honest. There are some great people in my life, I have some nice talents, there are things I still enjoy, and can do.
There are some people I can't hang out with anymore. There are some situations I need to say no to. There are relationships with things, people, places, experiences I had to end. That is my reality. But my reality is also that there are doors I can keep open, or open up, there are jobs I am fit for, there are ways I can be part of communities that I feel good about. There are things I can contribute.
I'm rambling now, hope this helped.