Akane's always been down to do anything for Ranma, but I like how this casually shows her strength, and that she spends so much time with him that his craziness is rubbing off on her. Akane faking cute, exaggerated innocence? that's not typical Akane. That's 100% a Ranma move.
Ranma knows Akane well enough to realize when she's not acting like herself, but he's so affected by what he thinks is Akane giving him affection and being forward that his only functional braincell takes a sabbatical.