Life is full of twist and turns and you never know where the next road will lead you to. I have personally done nice dinner and drinks with gals despite being married and if they are comfortable with you, they will agree to the next date and the next.
Barriers do fall over time and the woman once comfortable with you will reciprocate your initiatives be it hugs and kisses or a full fledged romp in bed. It takes chemistry to get to this point so don't set this as your main goal but rather work towards it.
At the end of the day, you may end up with a gal that will only your best friend. So let it be, she is still a friend worth having and to treasure.