get some good nice rich, organic soil and get some NPK nutrients. What I do is that I check them 3 or 4 times a day and if I stick my finger in the soil and it isnt at least moist then I water it. Haven't had a single problem so far.
I think confronting your parents about this first would be the best thing. If they dont approve of it then you dont grow. Just wait a few more years then grow in your own privacy. If you decide to grow without telling them and they find it then you will be in deep shit.
I think you should get...
Are you absolutely sure she saw you with the plants? If she thinks they were marijuana plants she might call the police... she might not. If she does then the police will most likely just get a search warrent and come to your house. The best thing to do would be to get rid of them now. ...