My ex boyfriend is dating
You also do not need to talk about her ex around her regardless of how close you are or aren't. If you have a close friend who is reeling from a break-up then you absolutely need to speak to her and talk to her about her feelings about you possibly dating her ex.
Initially you're best choice is to reach out via the web.
Creating the bonds of trust that the two of you never used to give a second though is imperative.
If he thinks you're likely to sneak behind his back and tattle on him he won't give contacting you another thought.
If you want to pull this thing off you need to use a woman's number one trick - a clever ploy to capture his attention and turn it away from his new flame.
Play It Carefully - Be Subtle You don't want to become too wrapped up in playing with his mind - no one likes to feel someone else's thoughts or ideas prodding around in there but sometimes playing dirty is the only way to get a foot in the door.
Right now your ex is swimming with an almost insurmountable attraction for his new girlfriend.