The author needs to move forward with the love triangle soon. I am pretty sure its gonna come soon with the other girl and her feelings becoming clearer for the MC.
But her comment once again reinforces his belief that she just sees him as a little brother as he overheard her outright say way back in Chapter 1 (in the Canon Pre-serialization). That was his traumatic blow because at the time he liked her and thought she might like him because she was extra friendly to him.