I think she genuinely means it when she says "It's not my fault I'm always crying..." Like her avatar is made that way, so as long as she doesn't have a mask on, she will be crying and she can't stop that whatsoever. Since the circus gave her avatar those tears; as soon as that comedy mask is off, she will be crying. Even if she isn't sad nor upset.
"I promise not to be annoying this time..." implies the members always found it annoying (or at least, it seemed to her that they thought so,) when she was ..."happy". Poor girl. She faced the same treatment in episode 4 with her (what I like to call) manager mask, so it's not very unlikely. Reinforces how it feels to have your happiness be "incompatible" with others'.
As for the brain rotting one, I don't know if it has any relevance. I've seen some connect it to the theories that involve their bodies in the real world rotting as they're stuck in the circus, though. I think that's notable.
Unrelated note. Is her mask floating? The ribbon and the mask aren't connected like they are in the show. I wonder if that was just a small design change for practical benefit or gooseworx just wanted to draw her like that.