Girl Problems should I tell her how I feel?

Okay, so me and this girl are really good friends. I talk to her everyday,we text everyday, hang out with her at least 1-2 times a week. I flirt with her, she flirts back and I really like her. I think she likes me, when I tell her I want to cuddle she says she would like to and she said that 4th of july would have been better if she had been able to watch fireworks with me. She said she doesn't plan on letting me go anytime soon. Lately though she hasn't been doing flirting as much, I think she may be losing interest in me and I don't want her to. I really like this girl I think about her non stop, I love her quirkiness, her funny mannerisms, the way she acts, the way she talks, her funny faces she makes, everything, I want her to know how I feel, but i'm not sure if i should tell her. Someone told me I shouldn't, but i want to. I'm not really sure how I should tell her though or where to begin. I want to tell her in person but she makes me nervous sometimes. Should I text her or tell her on the phone? Can someone please help me, I've never really liked a girl the way I like her and I don't want her to be a "what if". I would hate to lose our friendship but i don't want to be "just friends" with her, I want more. So I'm willing to risk it. I told her i had to talk to her something very important but I wanted to tell her in person, but she keeps begging me to tell her over text though. She said she wants me to tell her over text, because when people put her on the spot she changes the subject. But i fear that if i tell her through text she might not respond back?