] During this read, I confess I am wondering for the first time whether there is any sincere friendship from Isabella at all,

How funny - this is the first time I'm actually looking for some proof of friendship - I've never had a doubt before that there was none. ;-)

I think there was perhaps a spark of it. I see it in the glee they share over horrid books. Even while she is playing up to Catherine because of James, before he arrived, they did share a tiny bit of common ground. But it doesn't last long.

Perhaps this bit shows the only kind of friendship Isabella is capable of?

"I told Captain Hunt ... that if he was to tease me all night, I would not dance with him, unless he would allow Miss Andrews to be as beautiful as an angel. The men think us incapable of real friendship, you know, and I am determined to show them the difference."

And then she proceeds to prove it by dissing Miss Andrews in the next paragraph:

"...you have so much animation, which is exactly what Miss Andrews wants, for I must confess there is something amazingly insipid about her."

So yes, like Irene says, one must wonder what Isabella says about Catherine behind her back.