... and there might be something better for both of us in not continuing with this relationship"
^I agree with this... it allows a closer in this "relationship"... for you and the girl...
even though she will be hurt, she will understand that you are not attracted to her.
There is another thread going on - that's discussing how he is being totally avoided... If you are not attracted to her - the above statement will at least give the girl a closure - otherwise she will be very disturbed and continue to look for an answer... so with all respect let her know...