Vintage kids jean dress

A cute vintage hard to find dress with rainbow heart buttons madenof 100 percent cotton It also has a tag that says the number 7 so idk what thats about. (Shown in the pics) No stains, holes, or anything of the matter its pretty much in perfect condition. I got this for my cousin but shes having a boy i guess, so here i am. Even though theres nothing wrong with a boy wearing a dress .