Clarification here: He didn't "consent": He
insisted. His aunt is on the record that he was pushing for this stunt very hard and that both the girl (19) and his aunt were against it.
If they send her to jail I expect that she shall get a slap on the wrist and be out in as little as 1 year or even 6 months. There isn't the slightest hint of malice, etc, which is why she's been charged with 2nd Degree Manslaughter.
Second-degree murder is ordinarily defined as: 1) an intentional killing that is not premeditated or planned, nor committed in a reasonable "heat of passion"; or 2) a killing caused by dangerous conduct and the offender's obvious lack of concern for human life.
There was no "intentional" bit involved with this death and she and her aunt were clearly concerned for his life.
So while she might get jail time I wouldn't be at all surprised if she merely gets community service and parole.