How should I deal with a friend being insecure and competing with me over men?

First of all, she is NOT single she lives with someone and has a child with them. Everyone that shows an interest in me she pursues them relentlessly. I was seeing someone recently that I was very interested in and wanted to take it slow. He was someone she had introduced me to and said she had no interest in him. So she decided to send him flirty texts in the middle of the night. How should I deal with this? I really don't want revenge or to sink to her level.