Maud Pie, who lives in Ponyville now, finds a boyfriend. Pinky Pie can't stand him. Not only is he taking Maud away from her, he's incredibly annoying! She consults her other sisters, who point out that he makes Maud happy, and Pinky realizes that what matters is that Maud likes him. He even gives Pinky good advice on how to throw a party for Maud: with lots of advance notice and with Maud not in attendance.
I liked this. The rest of the Mane Six learned that lesson re Pinky herself, and now Pinky has learned it too.