Just got out of a relationship with a girl who had mild cluster B tendencies - mood swings, selfish, impulsive, lacked accountability, perpetual victim, the whole nine yards - and yeah it's definitely not fun, and you'll put up with alot of bullsh!t from your partner only to feel like her problems and decisions were all your fault because of her ability to manipulate you. She was definitely on that spectrum but I don't know if you could categorize her into a singular disorder classification, if I had to put a label on her it would be a mild case of borderline.
Anyways, my story with a cluster B type followed a similar pattern as most others in this thread - the relationship started out amazing, the sex was great, there was constant affection ("lovebombing" if you will) and everything felt perfect. Her and I seemed perfectly compatible and she liked all the things I liked and she wanted to change her personality to what she thought I wanted. This all lasted for about a year, until I started noticing changes and her true colors began to show. She would start fights over little things and began threatening to break up if she didn't get her way on things. Then she developed a pretty nasty drinking habit which lead to a DUI. This DUI prevented her from being able to get a job (we had just graduated college and she was trying to work as an elementary school teacher) and her life was in a complete tailspin with thousands of dollars of debt. Of course, she was taking her stress out on me and picking stupid fights about everything she could and was even physically abusing our dogs when she would get really angry (of course she didn't see anything wrong with making our dogs squeal in pain because she was just disciplining them). I put up with all the drama and fighting for over a year until everything came to a head when she tried to steal $500 from me in order to pay off her debts, which I caught her on video doing. When I confronted her about this half an hour after it happened, she said "oh I forgot taking that money, it must have just been a accident I was in such a rush at the time" and then accused me of having trust and anger issues when I didn't believe that it was just an accident. I broke up her that night, and I wish I could say I completely cut ties after that point, but it took months for me to stop blaming myself and wanting her back (or at least the "ideal" version of herself that she sold me in the beginning).
My advice: seek therapy or help from someone who can help you learn to have a more secure attachment style so that you learn not fall for these types, set boundaries, etc.