Starlow is nowhere NEAR on the obnoxious level of Kersti.
That said, I do think she's an ass to Luigi. A lot of people cite that she apologizes in BIS, but like, she only does that after Luigi is so hurt that Mario has to step in and stand up for him. She respects Mario, it's only his intervention that makes her apologize which is why I didn't feel it was sincere. Especially since she continues to be mean spirited to him in the next two games. The lore reason for the Luiginary abilities in DT is that Starlow is so pissed at Luigi that she attacks his face. She has no idea she's helping Mario in the dream world, on her end she is literally just taking out all her frustration on Luigi.
But by far the biggest offender is that one scene in Paper Jam where she goes out of her way to describe the misery of captured Toads in elaborate detail after seeing how much the idea upsets Luigi, describes them calling out for his help, then hits him with the "thankfully that's not realistic, they'd want Mario's help, not yours". She's only "nice" to Luigi when he's alone and she knows he's their only hope. Even then it feels like she's trying too hard to butter him up, none of it feels sincere after how she talks to him earlier.
Brothership dialed it back thankfully, and as a result she is much more likable in that game than in the previous ones. I know that Luigi being the butt of a joke is a recurring thing in these games, but in most other instances it's just someone getting his name wrong or not remembering him, which usually just makes him faceplant or something. Starlow drives it in hard and keeps going after she sees he's upset. The only other character to act like that in the series is the Star Gate.
