All those complaining about lack of sex with Erynn have to consider her relationship experience (or lack of it), one of the (if not the (we don't see anyone else)) only guy(s) she's had sex with recorded it and showed it round his mates. The guy who has shown the most interest in her other than the MC is a manipulative asshole who is attempting to blackmail her into having sex with him. It's not a surprise she's not looking to jump into a relationship or into bed with anyone at this stage, she is slowly coming round to the idea of a relationship and getting physical with the MC, her reluctance has to be expected.
It's clear she has some trauma regarding the situation, and that makes her tentative.I agree with the semtiment here but she's baiting him (MC). If you're on Erynn's route in her apartment when MC decides to help her in the case of video it was her who made kiss initiative in which of course MC returned. Then at MC place when MC showed her that game. Well one thing led to another, kissing, striping... and finaly in Episode 10 she's not sure in herself. She goes back and forth with MC. I think both of them need to figure what they want because even MC went on certain things unsecure. If you're on Erynn's route it's clear that there's chemistry between the two. I think that two of them should figure out are they dating like GF and BF or to remain just friends.
The first one i found acceptable because she had just been in another ugly situation and things moved fast from there.
The second one stopped by the "evil cockblocking mom" a lot less so...
This last one ends up on the MC who for some reason decide not to press the action, after the kiss he is the one who thinks/decides they aren't there yet.
Speculation on my part but i think Nyx wants some grandiose romantic/heroic moment rather than "and then they fucked", this is the storyline that forces us to play "knight in shinning armor" to progress after all.