I'm just going to say this, I'm not flaming you. BUT....

You seem a bit of a bone head.
To be honest, you wonder why this girls parent's dont want you seeing her?
In the past 3 days, you have posted about :

OD'ing on sleeping pills
Eating mushrooms, from people you've never met.
Chronic smoking
No signs of a life: IE, your 15, so you don't work, do you goto school? Or you a drop out?
Any wonder why your grandma won't give you any money?
You haven't done anything for 12 hours and your gettin some withdrawal symptoms?
My advice to you is seek help.
I like weed an other stuff, but I've been clean for the past 6-8 months because I've wanted to be, I'm growing my own and am gonna love that but I think you need to give yourself a chance.
This girls 15, if she was 25 or something I'd agree, the parent's should butt out, but she's 15 for gods sake.
How do you afford all your stuff then? Because I'm a 21 year old guy, paying a mortgage,food bills, utility bills, electric,gas,water,council tax, I just about have some cash to myself, so pray tell how you get all these things for free?
Or do you get cash from those "FUCKING PARENTS" who should only go to work to earn money, simply to give it to you?