The guy courted her and she fell in love with him ("You broke into my life/and stole my heart"). She performed oral sex on him ("sweet surrender found me/on my knees"), but he left her, perhaps right after that ("you left the scene of the crime/hit and run").
He wants her back ("well, now you're back again/and say you've changed"), but she's rejecting him, not because she doesn't have feelings for him anymore, but to make him hurt just like he made her hurt ("just like me you'll be/a casualty of your love").
Why did he leave her? She seems to think he was indecisive, not just callously using her ("without a single clue/you fell apart"). But we should consider that she may be an unreliable narrator on that point; maybe he really did just use her and is now trying to use her again.
The guy courted her and she fell in love with him ("You broke into my life/and stole my heart"). She performed oral sex on him ("sweet surrender found me/on my knees"), but he left her, perhaps right after that ("you left the scene of the crime/hit and run").
He wants her back ("well, now you're back again/and say you've changed"), but she's rejecting him, not because she doesn't have feelings for him anymore, but to make him hurt just like he made her hurt ("just like me you'll be/a casualty of your love").
Why did he leave her? She seems to think he was indecisive, not just callously using her ("without a single clue/you fell apart"). But we should consider that she may be an unreliable narrator on that point; maybe he really did just use her and is now trying to use her again.