As far as I know, she visits every two weeks or so and stays three days. You will receive a messenger when she does, but I think you need to receive it in Hawkethorne. I normally get it when I step out of the Waystone in the square, but it might hit at the gates if you walk in.
Then she should be available at the Wayfort Waystone (unless you miss her, in which case you will get a message that you missed her)