So in other words, Linnea made bad decisions and her death is her own responsibility.
Not necessarily -- and this is a difficult topic given the tragic outcome. Most of the discussion so far, though, has assumed that the factual allegations of the complaint are uncontested and that there are no other relevant facts. I don't know what the contributory negligence laws are in Montana, but even if the Defendants provided bad advice, if the Plaintiff was found to be more negligent than the Defendants it is possible that Defendants could be found not liable. I don't know, but would guess that lawyers for both the Defendants (possibly hired by insurance companies) and Plaintiffs have researched these issues thoroughly and disagree. There may also be a liability waiver involved (but we don't know this either way at this point).
If adults are to be permitted to engage in potentially risky pastimes (scuba, skydiving, mountain climbing, shooting\hunting, etc.), the cost of those activities will increase and accessibility will decrease the more we expect to be protected from ourselves. An example of this would be the certification requirements to dive in certain Florida springs. I'm not necessarily saying that it is a bad idea to require a full cave certification to dive in certain locations, but such requirements have increased the cost for those that want to do those dives and have decreased general accessibility. I'm not making a judgment here as to whether that's a good idea -- it might be. But there is always a tradeoff. If a teacher\student relationship is established, the analysis perhaps changes, but, again, depending on the state and profession, an adult might have the ability to release the teacher in advance from liability for the teacher's negligence.
I maybe had heard a reference to the shop renting equipment to an uncertified diver (maybe on this thread -- I'm not sure). Are there any laws that prohibit that? I can rent a handgun at a range and be given ammunition with few questions asked, and I know almost nothing about firearms. If I sign a waiver and then hurt myself, is the range responsible?