She's already said "Love Will Remember" is her sweet breakup song about Justin Bieber (from before they got back together, if they are even officially back together). "Birthday" may be a reference to her own 21st birthday, a milestone she'll hit on July 22.
"Come & Get It" was her first single, and she just released her second, "Slow Down." Listen to it here. What do you think? It doesn’t sound like she wants to slow down at all!