Jack Kevorkian helped terminally ill people who had made a rational decision to end their lives with dignity, was convicted of 2nd degree murder and spent 8 years in jail.
Lori Drew drove a (relatively) healthy young lady to make an irrational decision to end her life, was convicted of a few misdemeanors, and is not imprisoned.
These are entirely different scenarios and has a few errors. First problem is that Kevorkian's intention was to kill. Was Lori Drew's intentions to kill the girl or not? Maybe but you can't be absolutely sure. The most important problem with your statement is that the girl wasn't relatively healthy. She was already on medication with a known side effect of increased suicidal thoughts.
I have made fun of people and people have made fun of me. It has always been in good fun and I've never meant any ill will by it. If I say you are ugly and you go kill yourself, should I be held accountable for killing you? As horrible as it is, Lori Drew should be held accountable for harassment and not murder unless they can prove beyond a reasonable doubt that was what Lori Drew was trying to do.