Proceed with Caution
So, you’ve read the warning labels and still want to proceed. Great. If you’re in direct contact with the friend, then keep talking to her as if nothing happened. Don’t mention the breakup—don’t worry, your ex already told her everything. If you’re not in contact, add her on Facebook after a few weeks. If she declines, she wasn’t interested or it was too soon. If she accepts, start a conversation about something you have in common.
It’s important to treat her exactly how you’d treat any other new woman in your life. I had a client who came to me after making precisely this mistake: He assumed that he and his ex’s pal were past the whole get-to-know each-other part of the dating process because they already knew each other well. And indeed they did, in the context of him dating her friend—but not as potential partners. How you frame something with a woman matters—a lot. If you act like her friend’s ex, she’ll naturally treat you that way. If you act like a guy who’s interested in her, she’ll be more likely to see you in that light.