Both Catalina and Elliot are standing in that last panel, putting Catalina around Justin's height at the moment.
People have commented on Susan taking Rhoda's description of her well, up to and including wondering if the police or bunny card have a mental side effect.
Now, as per my standard belief that "if it's not said in the comic, it's open to interpretation", what follows is just my thinking, and it's entirely up to you whether you give a carp and accept it as the canon explanation, but:
Rhoda described Susan almost as a statement of objective fact (I know it's subjctive, step away from the keyboard) without any ulterior motives or attempt at manipulation. What would normally bother Susan about a compliment regarding her appearance would be those ulterior motives the unwanted flirtation, etc.
In short, by Rhoda being so matter of fact about Susan looking good, Susan genuinely felt flattered by it.