I'll echo stitchmaker here - given you went back to Sunday (ac day starts at 6am) it resets the visitors for the week, which I think explains why Gracie was not there when the day turned to Monday (well she could have been if the game set the visitors with Gracie on a Monday again) - you should find another NPC (which could be Pete/Redd etc) as the Monday visitor.
As stitchmaker says you might get lucky and see Gracie later on in the week.
Personally I would let the game play as normal, with the WA update, Gracie does appear more often so should come around again fairly quickly.
As to passing fashion checks - I've passed a check with just two items from the style she asks for, I just pick one other style which doesn't clash with the style asked for. She doesn't particularly like it and offers just clothing not furniture, but it is a pass.
What I'm not sure of: are the 2 pieces of the required style important - ie should one be an accessory plus say a shirt/dress?
I know accessories are important, plus a hat, but not sure if they always need to be in the required style - I don't think they do.
I know you can see her sockless if you haven't got socks in the asked for style.
Whatever you do make sure you don't go in a clashing style, automatic fail. (& that's it for the whole visit, alts won't be offered a check).
Modern does not clash with any of the other styles.
Its probably safest to keep it to just one extra style, eg modern + cute (or say modern + basic). She does say something about you are mixing it up rather.
You could always save before you go up to her for the check & if she fails you reset and try again. (I presume she would still be there).
And as stitichmaker says you can see her with an alt & hope for an easier check.
I've found two helpful posts:
the first one confirms two items from the required style is enough (in fact it goes further and says just one item may be enough, but never seen any confirmation, & I would say risky).
The 2nd link gives a solution to seeing Gracie again when she origianlly appears on a Monday (you TT forward and then back rather than the other way round; I don't know if this works or not - albeit confirmed as successful within the thread)
https://www.reddit.com/r/AnimalCros...es_fashion_checks_or_how_to_pass_by_the_skin/
https://www.reddit.com/r/AnimalCros...stion_about_time_traveling_for_gracie_checks/