That was my first impression, but I would feel the same way you are right now. WOW, WTF! is right. I have no idea on what you should do, but I think if my emotions were take over, I would jump back into it with ex.
My ideas being on the outside, I would continue doing what your doing with YOUR life. and not do anything intimate with ex untill you decide to actually start dating.
My fear would be she wants sex, and she had it with you so why not. Just things in my own head.
My advice, take it with a grain of salt, just be a closer friend than in the past, and see what happens down the road. But don't hurt the person who you are with now.
M-31 W-25 S-1 1/2 bomb dropped 9-01-06,and repeating over and over "I, not events, have the power to make me happy or unhappy today. I can choose which it shall be." Groucho Marx.
