Am I over reacting

My boyfriend was two timing me with this girl.. I found out and left him.. also the same girl was really bitchy to me in the office . She shouted at me without any reason in front of the entire office. I felt really depressed for a year because of that episode..I was really the shy quiet sort of girl that time.. so I just quietly cried in the restroom.. I reached home and had told the entire episode to my best friend.. it was her day off so she didn’t know what happened in the office.. if she doesn’t like someone I maintain my distance from that person too.. but today I found out that my best friend has been catching up for drinks with that same girl. I’m hurt. Am I over reacting