I think she'll be in the plaza all day on the day she comes. It might be different for everyone, but in my case, I saw her once a week until she agreed to open her shop. I don't remember if it was on a specific day, though.
Thank you all for responding ... I TT a few days and she showed up.
I took the advise given here and kept tt back one day then forward one day to the day she was here. doing the fashion check each time.
It worked perfectly ... got my Gracie's store and everything is hunky dorey in DupeTown.
Thanks again for the good advice ... this forum has really helped me with a lot of things.