I'm confused? Why exactly is Miwa considered a pain? Can someone please explain what makes her a pain? I feel like I'm missing stuff D:
I read it like this: She's a high maintenance person. She has a particular way that she's imagined certain things unfolding in her relationships, and when they don't go that way, she's just visibly disappointed. She's considerate enough to not boss people around to suit her whims, but she still overthinks everything and isn't good at hiding when she's unhappy.
Which means, basically, that her friends and girlfriend, who are relatively much more laid back and a little insensitive, wander into her little disappointments like a minefield and accidentally bum her out. And they know they didn't do anything wrong, but neither did she really. They love that she cares so much because it generally means she's a sweetheart, but sometimes it's just a little exhausting to deal with.