Literally says "They say you emperors are invincible" Is Big Mom not an emperor now? Also you ignore Law's dialogue about damage a page earlier.
and this where the 3rd grade level of reading kicks in. She's referencing to this:
Big Mom believes they're fighting for her spot in the new world, for their own ambitions. Kid(who this entire time has been alluding to the fame for beating a Yonko) admits he's now fighting to help Luffy.
It's seriously not that hard to understand, it's a character growth moment.
Yeah because she's losing. Do you think if Big Mom beats them she would just walk away? unless she loses she's not giving up killing Luffy.
I swear sometimes I feel like I am the only that can read here