Perhaps James thinks by now Catherine knows his motives, if not by observation then maybe Isabella has told her.

It is also possible that Isabella has tried to weave a story of how Catherine loves her so much especially because.....!!!!!!

And James is being a 'selfish' lover here, and expects Catherine to understand his reasons, and help him along in furthering his addresses to the fair Isabella.

I didn't get the feeling that he doesn't care for Catherine much - he's just too preoccupied, and to repeat, a selfish lover.

Another reason for not confessing to the true reason for being in Bath, I think could be that, perhaps they never indulged in heart to heart talks before. Remember she was a tomboy for a major part of her life, so most probably he's embarassed, and doesn't know how to tell her.

I do think James deserves to stand in the corner for this, and for skipping his attendance at Oxford, that's all.

They both think Isabella is great. Catherine begins to see a few things in her, because Isabella is not that much on guard with her as she would be with James.

As to James' friendship with John, I can imagine how it all started. Perhaps as new comers to Oxford they were both thrown together. It must not have been easy in such places to choose friends and reject ones who are available. I am basing it on the little knowledge I have obtained from reading.