The problem is that they didn't give Judy enough to go on. She was just the kid sister with the bratty zingers. That's about it. The only plot that had to do with her was just when she got jealous of Richie. I just wish they could have given an explanation for where she went instead of just making it seem like she never existed. Like she decided to live with Aunt Rachel since Rachel left the show too.
Indeed, it is like they had no interest at all in developing the character and making her interesting.