I failed a drug test?

Well I'm 14 and my brother and his wife are both in their late twenties. Anyway I went to stay round their house for a week because I was being difficult at home and my parents needed a break. When I arrived there my brother and his wife made a list of rules and the main rules was (1) no drugs (2) no smoking (3) no drinking and no adult material. I was shitting myself because they were being so strict on me even though I'm their family. My brothers wife is a doctor and she has a drug testing kit in her house. She then asked me to take a drugs test to see if she can trust me. But the problem is I have been trying a lot of drugs recently such as cocaine,cannabis and heroine so I couldn't really do it. But me and my brothers wife had a argument and it went on for two hours so I took the test just to keep the peace. It then came out negative and my brothers wife went ape **** and she started shouting and lecturing me. She didn't let me go out of the house on my own and she wouldn't allow me to have contact with anyone accept for my family all week. I hate her so much. Do you think she is a cow?