If you wanna chase a girl who is attached - you unofficially
'sign' a contract that already spelled out the risk and possible
hurt. Hanging out in middle of nowhere, having dinner, blar blar
blar, doesn't says ANYTHING at all. Really. Don't think too much
into the events. However, I am not saying that she doesn't like you
or whatsoever because its difficult to judge on my side. However.
the bottomline is: you could be generating pure company and certain
qualities that her bf may not have. This doesn't equate to love.

Seriously, since she is already attached - by right, she
shouldn't and couldn't remain emotionally/physically close to you
all the time. BY RIGHT, she will have a small little
distance, regardless of how comfortable she is with you. Previous
times, she didn't do that - doesn't mean she has to behave
in such intimate terms with you all the time for you ain't her bf
ya? 
P.S: I do not disagree nor support chasing attached girls; however,
please understand the package you are dealing with. By the way,
before you do anything, please please please - always consider your
status and position you are at to prevent foolish acts -
You are just a
friend. Therefore many pleasurable events that have took
place, is merely a bonus, not a must. 
Cheers