friendship issues

My apologies if this is the wrong place to post this but I need some advice. My best friend since freshman year of high school who has been my best friend for over 7 years now has been hanging out with the girl who used to bully me for my depression and anxiety in high school and I’m honestly hurt by it. The things this girl said to me still make me very anxious and I truly believe that “no one wants to be around me because I’m sad.” I obviously am okay with my best friend having other friends, which she does, and so do I. But her? The girl that my best friend knew really hurt me? I’m not sure if I’m being a baby about this situation or not. It sounds very highschool I know. And I have forgiven this girl, but what she has said to me still plagues my mind, and even in my relationship I’m thinking about the crap she said and I’m worried that my boyfriend will leave me because of my anxiety even though I’m getting help for it. Any tips on how to deal with this or should I just let it go and not worry about it?

Thank you!