Mitsuki having sex with Aya when she was so drunk and tired that she couldn't consent...
I think this is a slanted way to view c.167. You can be uncomfortable with drunk sex, but Mitsuki and Aya are in a relationship -- they have a pre-established level of physical/psychological trust, are constantly physical with their affection -- and, although drunk, Aya was the one pulling Mitsuki in. If Mitsuki had tried to initiate with drunk Aya, that would be a different story. To me the issue is less about the consent of sex itself (because, unless we go down a dark path, it will always be consensual between them), but rather the continued issue of "sex instead of communicating".
Unreliable, insecure narrator Mitsuki is thinking about how the only thing she can offer to Aya is her body -- we know this is false. Drunk Aya is in the clingy stage of her drunkenness and has been pining over her avoidant girlfriend all night, and she finally has a moment alone with her.