A lot of people, parents included, can't or don't know how to handle situations like that. Maybe she didn't think you were serious or were after attention, maybe she thought you just needed some space, or maybe she's just that self absorbed. I don't know her, so I can't really say. I do know that if my mom had done that it would hurt like hell. I've had people turn their backs on me and outright insult me when I told them I wanted to die, even as I was about to attempt and was trying to reach out to people I felt close to in order to keep myself from attempting (though looking back I know these weren't "real" attempts, but at the time they felt real).