Wise former employers limit discussion of former employees to date of hire, date of departure and job accountabilities. Subjective assessments are strictly a no-no in HR world. If it’s a touchy, difficult situation with a fair amount of he-said she-said, resulting in a termination whether voluntary or involuntary, they may not even allow your former supervisor the opportunity to expose them to potential legal action.
So, be honest but idealize the circumstance. Avoid negative personal obserations and keep it to facts, not subjective opinion. You had a few differences with your former supervisor, that led you to the conclusion that seeking other opportunities was the best course of action to take and you did so.
If you have good experience and no other examples of such a situation, it shouldn’t really pose that large of a problem. If there are other instances, you’ll appear temperamental and petulant to the potential employer and it will pose a problem. They’d hire you if you were the only candidate they’re able to locate capable of carrying out the responsibilities of the position, and they had a very pressing need to fill that position.
Speak the truth but put yourself in the best light possible. Avoid personal comments, your former supervisor is an abstraction to them. There are poor supervisors, they’re well aware.
Good luck.
It is my opinion that unless the x-boss is a ditz, she will pick up on the reason offered and let it go. Most former managers do not want themselves nor their firm to be sued.
All JMO