Being OOC, making extremely long posts and comments all the time (it's ok if you write lots, but when someone comments with 'hi' and you reply with seven paragraphs? it's a problem), over-explaining things to every single character even when it was OOC and ruined the fun (explaining every detail about the game to a new chara in a single post, doing things like tell Touya that his sister has magic when he'd just been told it's a SECRET and Watanuki would never tell something like that without permission, explaining to Kobato that she was just having a dream in an extremely vague post which shouldn't have made anyone automatically assume she was affected by the curse, letting know Yuuy and Fye about Himawari's bad luck and telling about the twin's past without caring that it's PRIVATE and A DELICATE THING and not Hokuto's business and OOC for her to reveal it), and being a complete drama queen, even with a character as Hokuto which doesn't act like that in canon (she got killed twice, bitched at everyone acting like a martyr 'cause she'd died for Subaru, told EVERY SINGLE CHARA she interacted with lately about her nightmare, even when it was absolutely random - if you want a recent one -).
I spoke to her about this thousands of times, explained in detail why these things bothered me and the players, tried to make her change. I warned her so many times, in the end I had to tell her that the next 'big' offense, or three smaller ones, would get her banned.
She made at least fifteen 'smaller' offenses and I still didn't ban her. But I told her to watch it 'cause she went ahead and told Yasha every detail of the game in one post, ruining the chance for that chara to interact that at least more slowly. When we talked that day, she asked me to tell her what she was doing wrong, I told her yet again. She promised she'd be careful and w/e.
And then told Yuuy randomly that the TRC!Yuuy had changed his name, something that isn't her business and wasn't necessary for her to explain, and even if she WAS BFF with the little Yuuy and Fye it'd make no sense for her to tell random people about it. Even Kurogane didn't tell the little Kurogane right away about what'd hapenn in the future.
So I told her she obviously wasn't ever going to change the things that bothered me, if after telling me she'd surely change she was doing the same things again. And that I couldn't ignore how this was ruining the game for everybody else just because I didn't want to ban her and appear as a bitch. I'd warn her enough times, gave her billions of chances, it was enough. She'd been told I'd ban her if she kept it up.