Monica's sister

So I know I'm late to the game but omg Monica's sister is absolutely awful. She seems so jealous of Monica and just so terribly pessimistic. She brought up that Monica had dated some dudes in highschool it's just nuts. I haven't seen if they tie the knot so maybe they don't make it, but I don't think that I'd I were Monica that I'd be happy with the way my sister acted regardless. She was a jerk.