Bravo/NBCUniversal/Getty ImagesCiara Miller might just be the queen of summer. And regardless of what’s happening in the Summer House universe, she always knows how to serve a look.Ahead of the sunniest season, Old Navy tapped Miller to star in a new campaign alongside fellow summer icons Paris Hilton, Kathy Hilton, Rob Rausch, and influencer Eric Sedeño. Inspired by all things Y2K nostalgia, the campaign celebrates the 20th anniversary of Hilto…