Raven is a side option (was backed in the kickstarter campaign) so it is
possible to select her at Christmas and get some scenes with her in the second semester, she's just much less prominent than the "main" interests. And like Big Steve in Horse Hall, most people will probably need helpful instructions in order to figure out how to unlock her mini-route.
The bonus side options that were directly backed are Luke, Manuel, Suki, Raven and Pastel. The ones from the voting are Corrinna and one extra that hasn't been publicly announced yet.
In the current build, the storylines for Raven and Luke are already partly available, and Luke's mini-route is pretty easy to access. Manuel and Suki I am still waiting for more information from their backers to figure out what they want done with them. Pastel is tied to Minnie's storyline, so she'll become more prominent later on that route
. The bonus voting ones I haven't yet figured out exactly how their routes will work, other than that you probably need to join the Poetry Club for Corrinna. Those two mini-routes might get added in last after the main storyline is finished.