This surely won't end the
sweetie debate, but it's added fuel for it, at least.
To be completely honest and revealing of horrible behind the scenes secrets (what else are commentaries for?), this comic was a very late addition to the story. I decided that while I wanted Susan to be in the dark and confused, enough people care about Matt as a character that I didn't want his intentions to be left hanging in a cloud of vagueness.
Of course, as a result of this, Matt needed someone to talk to. Having not previously established any friends for Matt, suddenly a friend had to spring into existence, so... yeah. Now this character exists. And she's friends with Matt. And stuff. And I don't think this is the last we're going to see of her, either. If I didn't know any better, I'd think she just sort of willed herself into existence and that's why this comic page exists.