Which, essentially, means that Mab was going to thrash convention goers until her minions could snatch Molly. Meaning one of two things,
1) if Harry's not at the convention the first evening, i.e. drops Molly off after bailing her out or just lets her have the cab, she gets kidnapped the first night.
or
2) if Harry doesn't cast his mirror spell there's going to be a whole lot more mayhem before Mab finally gets her hands on Molly