Does she like me? Why am I so scared to tell her I like her?

I have known this girl for a long time (as in 5+ years) and about 1.5 years ago I started to like her, of course I've had plenty of random 'crushes' so I thought nothing of this at first. To make a long story short, I'm 14 and she's 13, for about a year I have hardly been able to stop thinking about her, not that I's really want to... Anyway, we were at a youth event she wanted to sit next to me instead of her girl-friends. Not only did that rock my world, but she and I were joking all that night (all-night youth event) and I was feeling right on top of myself. I had everything right where I wanted it and then the event was over. She is a very beautiful girl if you ask me and very nice. Now I have some family issues with all this so that could be some of my problem... But most of the time when we go anywhere where we coincide, I have siblings/parents there... Then there is the predominant fear of rejection. I am about 70% sure she likes me too, but that 30%... We 'flirt' back and forth, but some of that is very low level and hard to understand. I have several issues of my own that I think would be a lot easier to deal with if I had this load off my back. So...

How would I make sure she likes me back?

What is a good way to tell her that I like her?

Parental issues??

The last thing I want to do is make myself look like an idiot in front of/to her.

Any sane, rational advice is welcome, thanks.