I have ptsd from childhood abuse and a past abusive relationship. I've been diagnosed by a psychologist. I'm still learning about my ptsd so please bear with me.

Could a person develop ptsd from one single tragic incident ( car accident, animal attack,robbery)?

If a person is bullied, talked down to, mentally abused by a person they see once a year, maybe every two years over a period of several years could that cause ptsd? The person visits 10- 14 days at a time. I have a family member who does this to me. Every time I hear they plan on visiting I feel anxious, upset, angry.