I'm not exactly sure where to cut in here so I'm just gonna reply to this one and whoever needs to read it can read it.
Andrea being in friends is imo kind of a spoiler for the fact we will most likely be able to reconcile Lana and her.
You can break it down like this
Main Girls- Obviously lewdable, with routes.
Side Girls- People like Sienna, Fang, Caroline, Selena, and Lana that already have lewds or will have lewds in the future but won't have full routes like a main girl.
Friends- Classmates that won't get lewd scenes with the MC like Mike, Vicky, John, and Andrea. The kiss between Andrea and MC is a tricky subject but I wouldn't call it a lewd because it's a plot device and gets interrupted anyway.
Others- People who aren't classmates and also aren't lewdable such as parents, Receptionist, and the Dean.