You're not going to die and you don't deserve to die. It's just that your head is not in a good place and it's making it hard for you by telling you lies like that.

Your daughter will be fine and she'll probably forget all about this. You didn't mean to upset her and once you realized you had upset her, you stopped. I think it's that music is such an important thing for *you* right now that you're giving the incident more weight than it deserves. She's not in danger and neither are you.

To be perfectly honest, I think the sheer intensity of emotion you're experiencing with music right now is part of your mania, and once you come off this high, it won't be so hard to separate yourself from that song. You know bipolar folks obsess about stuff that seems really super important when manic, but doesn't have the same effect when stable. I don't think it's "you" who didn't want to turn the song off for your daughter's sake. I think it was your bipolar being a jerk.

It's going to be okay. If you feel guilty about it, just pray for forgiveness and keep strictly kid-friendly music in the car from now on.

ETA: If you get to the point you can't fight the compulsion to drive off, it's time to hand the keys to your husband. They need you, and if your family is becoming afraid you're going to run away, then you should listen to them. They love you and want you safe.