Is it fair to turn down shows where you feel the lead actor doesn't deserve to be there?

Context: a director I work with(so far the only one available) has an overwhelming favorite. They're very personally close and she always gets the best part in the season's most complex play, regardless of type. Reasons this feels off:

1. Her work ethic is abysmal. She misses half of rehearsals, she always has some wedding or birthday to attend. The other half she attends she is universally late to. She goes off book the last rehearsal before the premiere .

2. Her skill doesn't make up for it. She always either underacts or overacts. In comedies, she forgets the funniest lines. In dramas, she bursts out laughing during her own monologues.

3. Her shows just....don't happen. Out of 3 where she had leads, two got cancelled before opening night because they sucked.The third, people were literally asleep during.

By this point, it's not even about wanting her parts anymore. It's about making sacrifices for a show I know it's not going to be succesful. The director is very weird about her. She simultaneously gives her extremely negative feedback AND seems to think there is some untapped fountain of talent in her that the rest of the company can't match. She'd much rather cancel a show than cast someone else in her place. I just feel like boycotting every show she's also cast in. Have you ever been in a similar position and how did you handle it?