Finding an Old Horror Movie?

So I have been looking for a horror movie for years now. I saw it as a child and the things I remember are:

• A group of teenagers in a car, they stop by a nasty looking shed by the side of the road because one of them has to pee, and then she discovers a super fancy pink marble bathroom in the shed.
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• They get to a forest, meet a crazy barbie-type lady who lives there in her little barbie house.
  

• A scene in a mansion at a long dinner table where people are getting beheaded.

I've been looking for this film for ages, I saw it as a kid.

Thank you all in advance!