I agree with you with the boring part, at least the parts about friendship. I enjoyed the explanations of the different types of exorcists and the summoning part, though as you say the missed a good opportunity to have Rin trying to do it.

The other side of it, if the "cute girl" character that currently pretty much sucks becomes a bit better as a consequence of her new powers, I'm all for this boring chapter early.

Now I wonder about the demon that attacked the girls and Rin and what his purposed was.