1) No difference in meaning - "why" and "what for" are synonyms. 2) "But she also" - here, "but" means in contrast to something in the previous sentence or paragraph "looked back fondly on the past" - to "look back on" means "to remember" "frowning" - her facial expression "as she described the rudeness" - here, "described" means "talked about" "she said" - this means the writer is reporting her words, but may not agree with them. "was rampant today" - here, "rampant" here means "widespread." So the sentence means: "But she also remembered the past, frowning as she talked about the rudeness she said was widespread today." Does that help enough?

the meaning of sentence (C) in easy English is she physically moved her lips/mouth to a 'frown ' 皱眉

oops!