She's referring to Harry's quote referring to Snape as "probably the bravest man I ever knew." I don't know how serious SIP is that it was only put there to appease James and Sirius fans, but she's convinced that JKR favors the Marauders and she's changed their backstory just to appease James and Sirius fans when it was starting to look like they were assholes. I'm not even sure if that made sense.
Oh, I see. Thanks for the help! Personally, I read 'probably the bravest' as 'definitely one of the bravest'. It doesn't matter if he's not DEFINITELY the very bravest as long as his bravery is noticed and honoured - and how do you quantify bravery when Harry's seen so many people, including himself, show exceptional bravery?