Why is my friend talking to my ex?

I found out that my friend has been talking to my ex. When I confronted her, she lied and denied it, claiming she had blocked him. But when I asked her to show me the block list, she refused. I’m cutting ties with her for good. We’ve had so many issues before, and every time I gave her a chance, she proved to be a liar—even though I’ve always been completely honest and loyal to her