We're getting a pretty good picture of what friendship with Isabella is like in these early chapters.

I like JA's list of the proofs of friendship:

"They called each other by their Christian name, were always arm in arm when they walked, pinned up each other's train for the dance, and were not to be divided in the set; and if a rainy morning deprived them of other enjoyments, they were still resolute in meeting in defiance of wet and dirt, and shut themselves up, to read novels together."

While Isabella's shallowness and flightiness are readily apparent, I do think I see some sparks of friendship there, that there is some caring on her part for Catherine. But things seem to change when James and John arrive in town.

Suddenly "faithful Isabella" doesn't talk to Catherine when James is around, and has no compunction about leaving her alone - "Isabella, who had been talking to James on the other side of her, turned again to his sister and whispered, "My dear creature, I am afraid I must leave you," - can barely find the time to talk to her - "James and Isabella were so much engaged in conversing together that the latter had no leisure to bestow more on her friend than one smile, one squeeze, and one 'dearest Catherine.'"