Twilight Sparkle thought friendship was supposed to be about picnics and songs, not fights and hurt feelings. She never sent a report about the reality being a mix of both, but she got close a few times.
Twilight shows up on Rarity's doorstep in distress, which isn't too unusual. Her admission that she's come to Rarity about romance is, however! Naturally, Rarity is all too eager to tutor her in love's ways. It's only practice, isn't it?