By being positive being vague and not having the time for her.
When she reaches out the entire conversation onus is on her
Her " hey i havent heard from you in a while how have you been."
You " awesome! i have been so busy its been crazy. Wonder few months but crazy busy.!!!"
Her " what has had you busy?"
You " you know the usual. Dating, work, family. The gym. Speaking of which i dont have much time what's up?"
The fact you said dating this will trigger her. Dating huh, so are you seeing anyone now?" She will gauge her validation by what you say here. GIVE HER NOTHING ZERO ZIP. Most guys give the girl the impression they are single letting her know she still stands a chance. This is a mistake. She sees your single status as lack of options. Aka she feels validated and she feels she won the break up. Do not do this.
You " oh yeah. Ive been dating quite a bit."
Her "who are you seeing."
You "hey that is a conversation for another time. I gotta go get ready for a date. We will catch up a other time. Bye 'click'
You end the conversation telling her zero information leaving her in the dark. Zero validation.
This will be 3 minutes or less. And this will tell her she is NOT a priority at all in your life
Then you resume no contact. Give her nothing.