like maybe she was alcoholic or something

I looked through the text and could only find something about her being in an "institution." I also don't think that Roberta's mom...

ever had any verbal lines? I could be wrong about that though.

a possible mute, like maggie, perhaps?

I don't think she's mute- it would be strange not to mention. But I definitely think "sick" could be a euphemism for something. Like the res

t of the story, I think it's purposefully vague and open to interpretation.