Most Helpful Guy
Tell your ex's new girlfriend about his advances toward you? Not yet, but I would threaten HIM with telling her the next time he does it.
If he does it again, THEN I would tell her. I'd do my best to keep texts, and recordings of him talking to you to show her at that point.
He'll learn... unfortunately the hard way.
Most Helpful Girl
I would. With screen shots, and tell her to put her dog back on his leash.