Okay in seriousness it actually happened to me. A girl I was going out with who wanted to get married wouldn't go away. When she found out I was engaged she made a serious reappearance.
I was very concerned as she was trying to meet my soon to be wife, and she was a vicious girl. No jokes there. So I just explained to her if she didn't disappear I was going to get very upset.
We went out for 3 years so she knew me well enough. Haven't heard or seen her ever again. Once they start stalking mate you can't remain friends. They will do everything to undermine you.