...

] ] I immediately felt a falseness. I'm not sure that Isabella cares for Catherine save as a welcome source of attention other than her sisters. I just felt no genuine affection from Isabella. She was pleased with Catherine because Catherine served her purposes.

] I agree here. ...I felt Isabella's professions of friendship towards Catherine were very shallow and not to be trusted. Just as I immediately liked Catherine I was immediately skeptical of Isabella. I think she (IT) is shows herself as a user and a manipulater from the very beginning of the book. Vicki I.

She is being used and endearingly happy about it. Here's another passage where this hit me.

Isabella having gone through the usual ceremonial of meeting her friend with the most smiling and affectionate haste, of admiring the set of her gown, and envying the curl of her hair, they followed their chaperones, arm in arm, into the ballroom, whispering to each other whenever a thought occurred, and supplying the place of many ideas by a squeeze of the hand or a smile of affection

I think Catherine is still sort of bewitched by Isabella and the idea of having an elegant older girl for a 'friend'. So while this exchange is sincere on her part, I can imagine Isabella's eyes searching the room for any impertinent young men towards whom she can direct her artful performance. Now and then she encourages Catherine since she makes for a nice darkhaired , less sophisticated counterpart to Miss Thorpe's more mature, blond feminine charms .

In chapter 4 in connection with mentioning the age difference (17-21) Jane gives a subtle hint on Isabella's being more experienced.
Miss Thorpe, however, being four years older than Miss Morland, and at least four years better informed, had a very decided advantage ...