What can I say to stop my mother from being so controlling? I'm 18 years old and I still get treated as though i'm 15.  

"I am moving out. I have a job and can pay for rent, utilities, food and transportation. What furniture will you let me take with me?"  Other than that, her house her rules.

In the scheme of things there is not a heck of a lot of difference between 15 and 18 in years .. My guess .. And this IS just a wild guess .. But I would dare to say your mother is not so much treating you the way she does in terms of your age, but I would think it would be more like in terms of your maturity level. Just because you are 18 does not mean you have suddenly become more mature. She probably still feels she has to tell you to do the things (or not to do things) she did when you were much younger, because you are not taking the responsibility to do it .. Or not do it .. Whichever is appropriate.  When you start acting like an adult, she will probably start treating you like one.

To be a good parent, your mother has to realize and affirm to you that the control that she exerted over you as a child was necessary then, but that she has an obligation to turn that control over to you, preferably gradually and willingly.

At 18, the "her house, her rules" is not a tenable position for her to take (unless perhaps if you are under house arrest or on parole).

Two adults should be able to come to a reasonable accommodation in your situation---and you have a right to request reasonable changes in her behavior.

Best of luck.

What is needed is good communication skills;

Communication is a vital tool that can.

1.  Help others understand you.

2.  Help you understand why what you want is being refused.

If you want to receive the privileges of a grown-up, it's only reasonable that you develop mature communication skills.  How can you do so?

Learn to control your emotions.

Good communication requires self-control.  The Bible states: "All his spirit is what a stupid one let's out, but he that is wise keeps it calm to the last".

The point?

Avoid whining, sulking, slamming the door or stomping around the house.  Such behavior will probably lead to more rules-not to more freedom.

Try to see your parents point of view.  Example:  Suppose your parents are reluctant to let you attend a certain gathering or party.  Instead of arguing, you could ask:

"What if a mature, trustworthy friend came with me?.

Your parent may still not grant your request.  But if you understand their concerns, you have a better chance of suggesting an acceptable option.

Obeying your parents rules  is like paying off a debt to the bank-the more liable you ate, the more trust (or credit ) you will receive it's similar at home.  You owe your parents your obedience.  So if you continually let them down, don't be surprised if they reduce or even close your "line of credit".  On the other hand, if you prove trustworthy - even in small things- your parents are likely to trust you more in the future.

Her house her rules

The parent child relationship is the only one that grows apart  as it progresses.  This is the way nature intends it to be from the very first time your child pushes your hand away to the time they leave home for good.  It's hard to relinquish the control parents have had all your life, in some ways you will always be mama's little girl but you need to sit down and talk to your mom because at 18 years old you should be ready to either go to college on your own or be trying to get some sort of training to help you pay your own way in the world.