Christina Perri scored a hit last year with “Jar of Hearts,” about walking away from a shitty relationship. The 24-year-old divorcée from Philadelphia knows the subject well. Her debut album is filled with a dozen breakup songs that barely hide the conflict behind her decisions. Backed by plaintive piano and pop-rock melodies that aren’t in a hurry to get anywhere, Perri sounds like Fiona Apple’s sullen little sister, brushing away guys and then getting all mopey about it. With weighty strings occasionally driving songs to the emotional onramp, Lovestrong is heavy-handed to say the least. Even when she loosens up a little and it looks like things could turn hopeful, like on “Bluebird” and “Arms,” Perri manages to find the cloud in the silver lining.