The quest log says "talk to Rika in the noon..." but talking to Rika just gives fluff dialogue. I will post a save (in Rika's room, noon)
This is the step I'm talking about:
-Chat with Rika in the at noon in her room while Gwen's not there until she talks about when Gwen comes over. (You need to have Rika controlled)
Most dialogue requisite in this game is RNG based, so you may need to repeatedly talk to them. Also, when including saves, might want to do the whole folder (for MV at least), because it needs the global or whatever, unlike earlier versions. -- Don't have the game anymore (deleted after I finished with it), so can't check the save anyways
Anyways, from what I read, of your post, it seems you're looking for help controlling Gwen, and as said before, just keep talking to Rika (not while being controlled; you need to be able to control her though, aka being able to strip her), until they say something about Wednesday/Saturday. This'll flip the switch (even though you may already know when). You may need her to be at level 1 (BJ) first, though I don't remember having her at that.
-- Also note, I think, it only has to be in her room, alone, rather than day phase. -- Think I was able to get the dialogue to show at night.
TL;DR -- Did you talk to gwen (at school) for her intro, and the quest to control her first? That's the first 'gate' to getting her. After that, it's just repeatedly interacting with Rika (after you're able to control her) to get the dialogue. then the bear on Wednesday morn.