The "Waaa!" at the end is "ぱぁぁぁぁ" in the original text, which is a sound effect for having a bright and happy look on one's face. This is either a creative difference or a mistranslation (the translator may have mistaken the ぱ for a は, which can be romanized as "wa" under certain conditions).
Since An is clearly wearing Summer Ichika's outfit, decided to just add the appropriate cosplay tags, feel free to edit or remove if needed though.
I always did swear Ichika and An could be twi nsisters in separate universes, they look nearly the same and even have the same voice actor/seiyuu, lol.