Green-haired dude tells his friend not to use his shampoo, friend uses it and freaks out when her blonde hair turns green: 'She said that I should have specifically told her it had green dye in it.'

She's not a very good friend. 

You have to respect people's space when you're staying over at their house. You can't just use all of their stuff and eat all of their food just because you're staying over for a week. They might tell you, "feel free to help yourself to anything," but there are obviously limitations on that, even if they don't say it explicitly. If I told a house guest to help themselves to anything in the house, I wouldn't think that would apply to my closet or to going through all the drawers in my bedroom. But maybe you need to tell people explicitly exactly what they can and can't do in your house! Some people require such clarity. 

If your friend or another adult specifically tells you not to say or do something, chances are they're not merely trying to control you but rather to look out for your best interests. In fact, the same truism applies to parents telling their children what to do. 99% of the time, they just want you to make a smart decision that helps you instead of hurting you. There are some controlling people out there, but they're easy to identify. If your peer tells you how you should order at a restaurant, then you might not want to be friends with them. But if you know and trust your friend to advise you in the right direction, it's a good idea to listen to their advice.