Pretty much the only way in most of the USA that one can "force" a bipolar (or any other person, I believe) who really NEEDS meds in order to function properly, into any kind of consistent compliance is to involuntarily commit them into a psch facility until they "get it". Then afte they are discharge, they have to get blood tests to make sure their med levels are consistent and they are following up w/their shrink to keep the behaviours under control.
Round here the only way this can be done is an affadavit that "The person is a danger to him/herself or to others". My sister-in-law is severely bipolar to the point where she cannot work at all any more, and we have slammed her into hospital (my brother & I) against her will, multiple times. Usually after she's tried (again) to kill herself. Her Pscyh is totally on board with that, and if we have to do it in, say, the middle of the night (which has happened) he comes in promptly and signs the orders next day before the "72-hour-hold" even comes close to expiring. He knows her pretty damn well after 6 years of therapy, meds, and all.
She has also threatened my brother (who admittedly can be a major asshole) with bodily harm,to the extent of chasing him out of the house w/a bat or a knife or whatever -Yikes- and has come after a neighbour as well. All this while she is in Manic mode; the Depressive bits are the ones where she holes up in her bedroom, phones crying in the middle of the night, and tries suicide.
She is gonna end up in long-term psychiatric hospital placement if she doesn't stay on her meds this time, and misses any more appointments w/her supervising shrink w/bogus excuses. B/c she's frankly ****ing scary without them. Yeow.
It doesn't sound as tho your sister is anywhere near as severe w/ the manic & depressive rollercoaster as my s-i-l. Sounds fairly OCD with the obsessions w/whomever/whatever to me, but I'm no doc.
But with that Alphabet-Soup # of diagnoses your sib has, it has to be hard to find the proper mix of meds to stabilize everything. Are your parents zero help at insisting she be complying w/taking her meds?
Sorry you're having to go thru this. It must be tempting to just isolate yourself from her as much as possible, poor thing.
And imo it wouldn't be any harm for you to seek out a decent counselour for yourself as well Sometimes they're pretty helpful in teaching coping tools to deal with the stresses of mental illnesses in other members of families.
Good luck and Cyber Hugs to you.