OOC :: Plotting, etc. Josie is obviously there, because she's one of the hosts. She made a point to personally thank everyone who came to either part of this and is hoping to make some friends/get to know some people there. She decided on attending the (muggle) Outlander school, so definitely assume any classmates there were personally invited by her!
Rose accepted the invitation on Lizzie's post and she dragged Lissa along to the spa day, too. They would have went to the dinner, because Rose doesn't turn down food!