There's a fine line when writing "dumb" characters. The more cartoony, the dumber you can make the character without you feeling sorry for them. Like Ed from Ed, Edd and Eddy, it was a very cartoony show so they made him REALLY dumb and you didn't feel sorry for him. This rides that line for me, so far it's on the funny side of the line but if they make her any dumber I'll just feel sorry for her and won't be able to enjoy it.
I felt the same way about Aho-Girl I just felt sorry for her, like she needed help and all her friend did was abuse her.