It may be that I need to familiarize myself with the manner in which people are allowed to introduce others to their own friends and acquaintances once having been introduced to someone themselves, but I have found it odd that it is taking so long for Isabella, James, and John to be actually introduced Mr. Tilney and his sister. I mean, I've only read through to Ch. 11 so far, but its been a few days since John and James joined everyone in Bath, and it was the same time that Mr. Tilney and his sister (and father) made an appearance, and yet we have yet to see them meet after a number of opportunities! So, no I don't think Isabella is after Henry. If she were, she would have met him a few days and evenings before she does.