She's going to testify against Jeane Palfrey, who ran the alleged prostitution business, saying that it wasn't so "alleged." And the phone records link this woman to Vitter.
You see how Palfrey's working this? Link the escort to Vitter, then Vitter is implicated in illegal acts. And will be called to tesify. And he has to testify for Palfrey that it wasn't money for sex. Crazy stuff.
(And Palfrey is suing the escort, along with several others, for "breach of contract" for having sex with clients. Really crazy stuff.)