Even self-asphyxiating "games" go wrong. (child of a family friend died this way)

I hate to "rank" self harm, but in the grand scheme of things, this is indeed self harm that has a high probability of killing her. Most other common forms of self harm, while damaging to the body, don't pose such an imminent risk.

Don't hesitate to call 911 the next time she engages in this behavior. She may hate you, but better she be alive and hate you than her be dead and you beating yourself up for years to come.