My theory for the next episode is that Sage kind of panics about her relationship with the MC.
We never saw the aftermath of her "passionate kiss" with MC after the guitar lesson, or what happened when she woke up after the nap in episode 6.
In episode 3 & 4 (telling Sage "we almost fucked" in ep. 4), when MC tries to push for a relationship with Sage, she pushes back and stresses that this is all about sex and being horny.
Given all the stress/grief she's under, I can see Sage's first scene in episode 7 showing her having flashbacks to the guitar lesson and after MC turned away from her, she frowned and thought to herself "what am I doing, I'm with Chad" and when she wakes up in MC's arms while sick, she has a similar confused reaction even though she's single again.
That preview scene of Sage in MC's bedroom. I think that will be a scene where Sage tries to reset the "boundaries" of their relationship and tries to once again make it purely physical.
Not sure about the preview scene with Riona/Quinn flashing the two. Like others, I think it's probably a nightmare/fantasy sequence.