I think unless you said you were hoping you'd hurt yourself by driving recklessly, like if she thought you truly were a danger to yourself and others, then she couldn't really do anything.

Out of curiosity, are you bipolar? I'm only asking because that sounds like it could be a part of mania, feeling invincible. Or is it more like you just don't care about your own safety/well-being, and that's why you're driving that way? Which would be more along the lines of depression. Just some things she could be considering, depending on how you explained it.