That woman clearly had some issues and that’s not your fault. I’m so sorry that you had to go through this. That would have been unsettling to me too. She was very unprofessional and the manager should have apologized to you for her behavior and even given you a discount!

There is nothing wrong with you chewing gum in public. I love chewing gum but it caused my jaw to hurt and my dentist told me to stop and I did that same day.

Try not to dwell on this too much. You did nothing wrong.