Johny Explained things perfectly.
well for what it;s worth heres my side:
Being her friend (best friend) means you two should be physically comfortable, right? that means you can kino all the way with her all the time. It also means you can talk about anything. Basicaly your bother comfortable with each other.
Alright ama just put it out there, SEDUCE HER! not openly but "as friends, discreetly"
When watching a movie or being together, just kiss her on the cheeks randomly until its comfortable for you two to kiss anytime anywhere(ok with some exceptions

)
Touch her, sensually, her weist, neck,head arms, sometimes legs, basically places that isn't too close to her sexual organs, the SAFE ZONES. Touch her privates and she might freak if it's way too soon. start out with small not so noticeable caressing and build a seductive "motion." The motion, well you have to "feel it"
Bite her... neck, ears, some parts of her arms, etc.(safe zones)
EXPERIMENT, what she likes, her reactions, etc. never goto far, so stay from her butt, vagina, breast and possibly legs.
Escalate and NEVER push yourself, she has too OK it, she won't say "ok" or "thats good" but you should see how she reacts, it the sign's green keep going otherwise, stop or slow down, then slowly escalate again, But DON"T PUSH IT!!
Your goal is to get her horny. Once done, I dont know how she reacts when shes turned on, hopefully you'll find out
**Johny made a lot of good points**
1.Your offering her a Good time, not forcing
2.Cut the "i love you" BS out, biggest relationship killer, she might just want some fun..thats all.
3.DON"T FOCUS ON HER. You have a life now, right? enjoy it, meet other people while still messing with your "friend"
4.DON'T RUSH, rushing also ruins things
that's all bro, hope i helped