You're currently in the friend zone with this girl. You're the nice guy!
I've been in similar situations too, where I started liking a girl after thinking she was interested in me because of all the IOIs she's given me and all the touchy/feely/close encounters we've had.... but all that can lead to nothing if you don't build sexual tension between you guys.
Right know you don't know if she likes you or not. You're just guessing. There's probably a chance since she likes hanging with you and is playful sometimes, but you have to become more aggressive and playful yourself. (When I say aggressive I don't mean forcefully try to kiss her in surprise... that usually won't work)
My mistake has always been trying to seduce girls by being social and friendly. And it doesn't work. You have to be seductive.
Next time she hangs out with you... build some tension between you guys and make her feel a little uncomfortable. Have you ever been in a conversation w/ a girl where after you guys stop talking there's silence... and did you ever feel the need to say something to kill that silence? DON'T. Don't try to entertain her.
It's easiest to be seductive while listening.
While she is talking keep eye contact with her. Your face expression should be relaxed and calm. You should be layed back and just enjoying her beauty.
When you both stop talking there's tension right?
Don't feel the need to fill the vacuum by re-starting the conversation.
You're just killing the tension...
She will try to bait you, by giving you the "why are you looking me like this" face OR by verbally asking you "what is it?" or "why are you looking me like that?"
Ignore her!
or just say "I'm just looking at you" or "I'm just enjoying the view" or something like that;)
Now the whole point of escalating the vibe that way is to find out if she likes you.
After you unveil that tension you have to make a move.
Usually guys will go for the kiss which can lead to a harsh rejection.
or they will escalate verbally by telling her she's so beautiful.. those are both wrong.
You need to progressively but smoothly move closer to her, give her some sexual looks in her eyes or by looking at her mouth... you don't have to stop talking either, just talk slowly and use a lot of pauses. Don't seem too interested in her either. You need to get into that close/touching situation again, and you have to escalate the touching step by step and slowly so it does not seem awkward or out of the blue, which will cause her to be defensive (like when you went for the kiss randomly).
This kind of sexual tension build up is to see how she reacts to your small IOIs, if she's comfortable with you, she will probably not move away when you initially get closer or just caress her arm a little bit. And as you increase each escalation level, the next level is not as big of a leap and much easier to do. So next time you go for the kiss make sure you're at the stage where your cheeks are rubbing or your mouth is really close to each other.
Here's an awesome escalation video series:
http://www.youtube.com/watch?v=5DsVwYqVhdU
If you watch this video, you will know exactly what I'm talking about if you're kinda confused. All the videos in this series is GREAT and helped me out a lot.
Good luck buddy! I hope this helped you in any way.
Remember, don't ever verbalize your escalation by saying you like her or that she's beautiful! Don't give her any compliments. You already showed her you liked her by trying to kiss her. That's ok. I would suggest you be more cocky and indifferent around her, say some asshole remarks here and there, be a little mean to her but make her laugh too. You can even make a joke about that time you awkwardly tried to kiss her (baller status right here!)... because for some reason you thought you were with mila kunis or something lol.
And don't be afraid to build sexual tension or making anything awkward because you want her, and you want to be MORE than friends, so that's what you gotta do. If you just try to entertain her and be her friend when she needs you.. you will just remain in the friend zone. And the friend zone sucks when you like a girl.