Scary person

There is a person I work with who I’m scared of. I don’t see her often but I think about her a lot and imagine that she is going to give me a hard time or yell at me. She’s never actually even raised her voice to me, she’s pretty nice most of the time. But it’s like a visual of her pops into my head and I feel terrified like I’m about to be called down to the principal’s office. It feels irrational even though she has been stern with me in the past. I take it way too personally and feel afraid of her. I’m not sure how to change that association.