The thing to keep in mind about the case in question is that we only know even the vaguest details about the very last exchange the two had: when she tells him to get back in the car. Prosecutors obviously released this part to the public because it seems the most shocking and damning. But even if we isolate that and ignore the context of the hundreds of other messages (to me, these would make or break the case for criminal charges) should it really be a crime.
If a buddy of mine texts me saying he's about to swallow a whole bottle of sleeping pills and I write back "do it dickhead", can anyone but the two of us have the insight to know if I'm actually encouraging it or if I think he's just making up bullshit?
And before anyone says that it should always be taken seriously and only a terrible person would even leave open the possibility that it's some kind of sick joke: perhaps, but to wormwood's point, is it appropriate to make all terrible social interactions illegal?