Combined with what you pointed out in your post; Isabella's True Colors: "Isabella “gave her lover a flat contradiction, and once she drew back her hand” during their (Catherine & Isabella’s) parting interview" and the information we read as cited in this post, Isabella seems to have made a complete U-turn. In the beginning she was consumed with seeking and returning James's attention in what eventually became an obvious quest for a proposal and nearly in a faint waiting for Mr. Moreland's consent to acting like she would like to have a hole open up and swallow James.

Although Isabella had danced with Captain Tilney producing some concern for Catherine and the reader, the big turn-around seems to have come on receipt of the Mr. Moreland's consent which contained the financial stipulations.

First Isabella has a grave face, despite her words of 'charming indeed'. As the conversation continues she says,
"Nobody can think better of Mr. Moreland than I do, I am sure. But everybody has their failings, you know and everybody has a right to do what they like with their own money." Catherine was hurt by these insinuations. "I am very sure, " said she, "that my father has promised to do as much as he can afford." Isabella recollected herself.