She simply does not respect your boundary yet.
She gets a kick at knowing that you are still emotionally hooked on her. She want to make sure you don't forget about her.
Remember: psychic attention is energy!
When you think of her or she knows she still owns you, it gives her a sense of power.
If you want to get your message through, you need to be consistent and repeat the message a few times in various ways until she gets it. You need to be firm and consistent if you want her to stop. She needs to hear that 3-5 times until it really sinks in her.
You can as well simply delete her messages or not return her calls. She will eventually give up if there is no response.
Makes sense, right?