I agree with bluesummer's post (Wow for 10 YEARS??? - that blows my mind -that makes her almost part of the family hehe)
The other thing to think about is the moving on bit (And move on is something you will have to do regardless of whether you like it or not). Chances are, when you are ready to move on (If it's not now) your NEW friend will not be there for you (Because i think she will just get tired of waiting for you to come around). Wouldn't you rather move on, while you have an opportunity to move on with your new friend (Considering that she is attracted to you) or would you rather move on later on by yourself?
The hardest bit for you is to forget the past and treat it as a wanderful memory (But no more than that). My advice for you is to concentrate on your new friend. Dedicate more time to her and maybe with time you will develop more intimacy for her. Trust me, the easiest way to forget is to occupy your mind with something else. If you don't think anything will ever happen between you and your new friend then i think you should probably stop leading her on and let her go...
In any case, hope above helps!!!
Don't cry, don't regret and don't blame
Weak find the whip, willing find freedom
Towards the sun, carry your name
In warm hands you are given
Ask the wind for the way
Uncertainty's gone, your path will unravel
Accept all as it is and do not blame
God or the Devil
~Born to Live - Mavrik~