You’re right that grammatically it would be far better to continue in the same tense, though ‘have to’ wouldn’t work there. instead, the options would be: ‘had to’ and ‘we’d’ or ‘has to’ and ‘we’ll’.
In this informal conversation the change of tense indicates Jerry’s mind shift between the two events: her coming to NY for a seminar and the subsequent consequence of that – the two of them meeting.
Just to add some worthless trivia to Bees’ clearest explanation, I’d say why ‘have to’ doesn’t work here but ‘had to’ does is because the short distance between ‘she said’ and ‘she had to’ does not allow a conspicuous inconsistency. In this sense, ‘we’ll get together’ is far away from ‘she said’, and thus given a little ‘allowance’, or she just forgot about the tense set up earlier by herself.
Of course, ‘the subsequent consequence’ is most convincing.
LOL… and there was me thinking that ‘have to’ wouldn’t work because it matched the 1st person singular and not the 3rd person singular, which is what is required.
I think you’re a bit of a wind-up merchant, James.
“A wind-up” is British slang for an act of teasing. So a ‘wind-up merchant’ is someone who teases others, especially more gullible people. It’s meant more as a joke and in fun than as a means of causing hurt, though of course, as with all teases, it can backfire.
By the way ‘wind’ is pronounced as in ‘wind a watch’ not ‘gusty wind’.
An often-used colloquial pattern which is equivalent to the more standard ‘there I was, thinking that…’ and the even more correct "I thought that…’