I feel you on this. I've been waiting for her to come for about 3 weeks now. I've had Katie A LOT in my town, for no apparent reason. She's actually been there a few days a week. So I think that might have something to do with it.
That time travelling trick is really neat! Once she shows up I'll have to try it! In the meantime I guess we just have to stay positive and patient :/
Also when you do get her to show up, you can do all 4 checks in one day. Do the first one, then TT backwards to 5:59 am. When the day rolls over, you'll be on the same date & Gracie will still be there with a new challenge. Do the new one & repeat until you do all 4.