This would be a classic call for help or attention, not a serious attempt.
Taking less (15g at most) than the lethal dose (20-25g), not taking anti-emetics previously, and above all doing it in a sole bathroom while living with parents - could only mean this person did not really wish to die, which is perfectly fine, "boredom" is certainly not a legitimate reason to end such a young life.
But this could barely be called "a failed attempt". It was not a serious attempt and was destined to fail from the very start.
Get your act together and try to fix your life, because that is what you really want to do.
The "next time" and "an EVEN BETTER attempt" would have to involve a lot more determination, preparation and planning.
Postpone all this for some time, and give yourself several more YEARS, because one day this may very well be just a bad memory.
Attempts like this one don't prove anything about the lethality of the SN method.
It's like jumping from the 2nd floor on grass or cutting one's wrists sideways and calling it a "failed attempt".