She's the champion of a division (well it's not really a division, you need more than one average-at-best fighter for it to be a division), and that's the way it works, champions get main event status.
I am sure this division *cough, ahem, cough* won't be around this time next year or the year after, but for now it is what it is, champions main event, that's how it rolls and that's how it should be. Honestly, this whole thing is a waste of money until they get more fighters that have names, I literally know 1 person in her whole "division", and that's her, and I'm a huge MMA fan. The mass majority don't even know who she is I'm sure, much less whoever they find to fight her.
Anyways, at the end of the day and the bottom line she's the current champion of that "division", thus she main events, that's how it goes people.
“Anna, my strong, terrifying Anna.” -Cas
"You lack the requisite spine and testicular fortitude to study under me" -Elodin