Honestly, I would say she actually tried a lot.... she asked Tamaki 1) does she not like being touched/does she not want to reach climax, 2) does she not like touching Miwa, 3) if they could distance themselves since she would continue to lust after her, despite Tamaki's clear dislike for continuing intimacy when Miwa gets going. Miwa was pretty clear to Tamaki that she needed that continued intimacy to feel like Tamaki still loved her. There was pressure, but Miwa seemed like she tried really hard to keep that pressure off of Tamaki.
Girl tried harder than I would've if my partner didn't match my drive, and she really really did try to compromise, but Tamaki has a near nonexistent libido whereas Miwa has an extremely high one. It was just not something that could've worked out, and neither should take the blame for it libido-wise.
My biggest defense is that I actually think Miwa took it pretty well-- yes, she definitely gave up, but also uhhhh she was traumatized in the course of things--- and despite that, she broke it off decently with Tamaki, caring for her feelings up until they said their final goodbyes.
