How is Anime Impulse gonna feel when they find out that Niji knew Selen wouldn't show up to the event because they suspended her on Christmas, but didn't tell them until 2 days before the event (and called her absence "unforeseen")?

Because a lie like that, even if it's "only" a lie by omission, is not gonna help their business relationship. And I don't think that AI (or any other convention) would sell tickets to a meet and greet that they knew was not gonna happen, even if they did offer full refunds once they found out it wasn't gonna happen.