It's interesting, Francine really did start out in the books as primarily a bully and antagonist.  This is before even Muffy hit the scene, back in the fabled era of the 70s and early 80s.  First, she made fun of Arthur's nose, and then his glasses as you mentioned.  Once Muffy showed up and assumed the role of key antagonist, Francine grew into more of a frenemy, and then finally into a platonic best female friend.

An evolving little monkey, indeed.