] When they first meet in Bath he is very eager to renew the acquaintance.

I got the impression that James came to Bath with John expressly to "run into" Isabella. When the four young people arrive at the Allens', Catherine & her brother have this exchange: (Ch. 7)

"...I never was so happy before [says Catherine]; and now you are come it will be more delightful than ever; how good it is of you to come so far on purpose to see ME."
James accepted this tribute of gratitude, and qualified his conscience for accepting it too, by saying with perfect sincerity, "Indeed, Catherine, I love you dearly."

I read that to mean he didn't want to admit that she was not, in fact, the reason he came.

] I think more happened between James and Isabella during that week's holiday at Christmastime than we know.

Very possibly!

] I agree to all this, except the last bit - I don't see anything mercenary in her methods - yet . She is doing her best to attach him, but I don't think we can ascribe a motive as to why yet. She may actually like him for himself. (again, from what we can discern from these 8 chapters.)

I wondered right at the start if her immediate interest in Catherine stemmed from her wanting to get close to James' sister. It seemed a bit odd for her to be so avid for Catherine's company so quickly. As for setting her cap for James, she could like him for himself, but I guess I find her a bit over-eager and therefore I don't entirely trust her motives.