I’m working on finding that balance because I tend to jump from complete apathy and anger at her to guilt and pity.
It takes time. This is not a one and done sort of thing where you think about it, find an answer and everything is all set. It takes practice, dealing with our feelings, time to understand the dynamics of the disorder and how that plays into how we respond, etc. Even then, these relationships are very trying at best.
Setting boundaries has been completely exhausting and honestly feels pointless because she doesn’t respect them.
Boundaries can take a lot of time and energy and once you get comfortable with them and better with them it gets easier and less exhausting... most of the time. If however, you are waiting for her to respect them or follow them or even to hear you and recognize your needs, the exhaustion and frustration will continue. So lets talk about this some more.
Boundaries require no action on the part of the other person for them to work when implemented properly. Boundaries govern us, are a reflection of our personal values and how we choose to protect them and determine how we respond.
Expecting someone who has an emotional dysregulation disorder with poor impulse control and emotional immaturity to respect our boundaries is not going to be successful. As the healthy/healthier person it is up to us to take set and enforce our boundaries.
If you don't want to do the above, that is okay too. Recognize though that it is not necessarily the boundaries that did not work but that it was a choice you made, a choice that is valid given your needs and circumstances.
it is okay to say no if that is what you choose.