Hmm, is it gonna be that it was actually her, not her brother, that helped him (the story's ml, forgot his name, letio or something?) in the past, which she forgot happened, and he's just pretending not to know who she is right now? Could explain all the blush-iness and insistence on helping?
That, or my guess is completely wrong and he's just a very excited character lol
I know she's hiding her skills in order to survive, but I really just want her to show how good she really is just to shut them up lol it's not gonna happen anytime soon but one can still hope!