depending on your craft level, a plush or charm would be cool!
or you could always order something off etsy that someone else made by themselves, lol
Attach a letter using the Animal Crossing themed stationary!You can use inDesign or Photoshop to make it!
I don't know how long your friend's hair is, but you can attach some jingle bells to a hair tie or ribbon so that they can put it in their hair like Isabelle.
Send her some ambiios or whatever