Call it a hunch, but when I saw photos of the vegetation Shannon would have entered I could not (and still cannot) envision any earthly reason why I would go in there unless I was in fear of my life, or very stoned. Now, such a wide spread between possibilities (and theoretical ones, too) don't really get us too far in terms of process of elimination, but one thing I would point out is that while they are not mutually exclusive - you can quite easily be stoned and under threat, obviously, but equally it is quite possible to be so stoned that you BELIEVE you are under threat - either from someone who isn't there at all, or even from someone who is actually coming after you to try and help. I've seen it, and it's not pretty.
The removal of her jeans and them being found around half a mile from where her body ends up is a very curious detail - I don't really have a solution to propose but it is an aspect which certainly shouldn't be ignored. It is hard to envision any scenario whereby she was not the one who removed them herself for whatever reason, which again doesn't seem like a very rational thing to do for someone responding appropriately to a dire threat. Once again we come back to either the threat was there but she wasn't responding appropriately towards it, or the threat wasn't there at all which means she wasn't responding appropriately to her environment. And as an aside, if someone WAS chasing her presumably at a short distance and she stopped to remove her jeans, it seems odd they didn't manage to catch up with her then or shortly after but still needed another half a mile or so to do so.
Be it issues with her prescribed meds, or recreational drugs (and then be it PCP, Spice, Ketamine, or whatever), or alcohol, or a mental health crisis...etc...or a combination,nit nevertheless seems difficult to me to imagine that there wasn't SOMETHING up with Gilbert's brain chemistry at that point.
I happen to be acutely aware of issues of victim blaming, and of being disrespectful to the victims of crime in discussing their lives and so forth - but equally I don't really see why certain people with an interest in this case seem to see it as such an awful value judgement if anyone even entertains the possibility that Gilbert may have taken drugs on that night, as if they need to protect her reputation or something. Given her line of work I think it's more than likely she took most things she could get her hands on; I know I would. That doesn't make her a bad person, but we can go down a lot of blind alleys if we attempt to paint her as a saint.
And are some of the things that have been said about Dr Hackett without any proof (including on this thread) ethically any better? I'm not so sure.