Decision was a no. By 8 last night she expected to
reply.
I think you should at least include your reason for saying
"no".
When we punish children, we explain to them why they were being
punished, so that they may learn.
Let her know that, after her spiteful attempt to
discredit/dishonor you, you have no obligation to help her out.
Else you will only be confirmed as the kind of jerk she's been
telling others about.