If you are a genuinely good guy with good intentions then you have nothing to worry about. However, if you have any intentions that might end with the girl getting hurt then you better hope that her friends aren't crazy. Every girl you encounter will have her best friends, and of course they are protective of her, but some girls have best friends that are actually crazy and you really really don't want to mess with them. These are the friends that will actually key your car, egg your house, and tell everyone in town what type of awful person you are. Is it the most mature? Definitely not, but the crazy friends really don't care. These friends will actually do anything for their best friend so be very very careful if you think you're going to treat their friend like anything but the queen they think she is.
1. They know everything and have no boundaries
Once you start seeing a girl, if her best friends are crazy then fully expect that they have already stalked you and know everything there is to know about you. They know exactly who your last girlfriend was and what club she was at yesterday. They know everywhere you worked, your favorite bar, who your friends are, what car your drive. They know things that it doesn't even make sense for them to know but sure enough they do. So don't ever try to lie to them because the will findout and then you are really in trouble.
2. They are extremely protective
All friends are protective over the people they care about, but crazy best friends are much more protective than most. Even their friends sometimes try to get them to calm down but it never works. They will do anything to make sure that their best friend doesn't get hurt. The girl you are seeing is obviously someone they care a lot about and so I wouldn't mistreat her if you don't want them coming after you.
3. They will likely follow through with their threats
When someone hurts their best friend they become like a giant hit team. They don't care in the slightest how immature it is to key your car, egg your house, or (if they are really crazy) they might even try to confront/fight you in front of everyone you know. They will come seeking revenge for their friend and they will make it look like they weren't even in the same state at the time. You will likely never catch them, they become like special agents when trying to get justice for their friend. Even if the friend says it's okay and not to go after you, they still don't care. Screwing over a girl with crazy best friends is basically screwing yourself over in the end.
4. They will not hesitate to tell you and their friend that she deserves better than you
If they don't like you then they will not keep that to themselves. If they don't like you then you will know that, they aren't ones to keep it to themselves. They want you to know that they don't like you and that they will be watching you. They will
5. They will do anything to make sure that their friend doesn't get hurt
This doesn't need much description. The crazy friends will go to very extreme measures to make sure nothing bad happens to their friend.
6. If you hurt their friend they will likely seek revenge
If you hurt their friend they are not likely to just let it go. You should fully expect them to come after you seeking justice for their friend. It may be them telling the whole town that you are bad in bed, it may be them going all Carrie Underwood on your car. It depends how crazy they are and how badly you hurt their friend.
7. They will back her up no matter what
She could decide that because you mistreated her that she is now going to try to sleep with your best friend, and her crazy friends will back her up all the way. They will make sure that she doesn't do anything to seriously hurt herself but if she wants to close down the bar every night then you bet they will be right there beside her.
8. Did I mention that they are crazy?
You don't want your car to look like this, so do yourself a favor and don't mess with a girl with crazy best friends.