First of all, hugs:
I'm sorry to hear things are so rough for you right now.

I had a similar problem with talking to my parents about my depression. I wanted to see a doctor for a long time, and I wasn't going to say anything to my family until I got a diagnosis. But for some reason one day I just blurted out to my mom that I thought I might be depressed -- I was absolutely horrified, afraid that she'd say I was being weak or silly (which in retrospect, I doubt she'd ever really do, but I have a way of blowing things way out of proportion...). After I got my diagnosis, I decided not to tell my dad because he's not very big on mental health -- he just doesn't understand it very well.

The thing is ... there's no hiding this from the people closest to you. It's possible for a while, I suppose, but if you think that your parents have noticed something is wrong or different with you, then you're probably right. The bottom line is that you need help, and although it's scary, think of how much better things will be once you've gotten it! Depression is highly treatable, and you deserve to be happy and do what you need to in order to be well again. If you're afraid that your parents won't support you in needing help, then what about talking to someone else first? What about at school? Talking to a counsellor might be a good first step; I was seeing my counsellor for three months before I finally told my dad about my depression, and she coached me in how to go about doing it and gave me the confidence to tell him. The only advice I can give on telling is ... just do it. Obviously it sounds easier than it is, but the best thing is to tell your parents that you want to talk to them, take a deep breath, and go for it. It might help if you make a written plan of what you're going to say, or run it by a friend or counsellor first.

The last thing is that I'm sorry your friend is having a hard time dealing with your problems, but it's all the more reason to find a way to get help. Try not to be too hard on her; she's not a professional, so while I'm sure she cares about you and wants you to be well, she also probably has no idea what to do with the things you're telling her.

Good luck!