Nobody will always get along well, all the time. Martial arts are particualrly odd, because in the midst of practicing how to main people, we also develop relationships with our students...making the "mad about town" thing feel like a bit of a betrayal.
If something went south, and the student had moved on with ire, there is not much to be done if you have already given patching up the distance the old college try.
Sometimes, the best answer is to just busy yourself with living well, and continuing to pursue your own best excellence, while mentally releasing that person from your world...abandon them to their fates, be it fame & fortune or failure. Disconnect, and invest your energies elsewhere.
The truth has the ability to stand on its own; focus on maintaining your own space, and time will bear out the best ending. Many angry people left to their own devices self-destruct. All you have to do is outlast them. Something in the Tao about "endurance is to perservere?"
Dave