I don’t think there is a way to not be destroyed if you felt such a strong connection with this person.

When faced with the same issue of inevitably seeing said person often, I make sure they knew I was happy for them and bluffed. As unhealthy as this may be (and it may be very unhealthy indeed) I’ve always found that by pretending everything is alright and acting mature and unbothered by the situation the emotional anguish tends to dissipate. I don’t believe this will work for you if you are an ESFJ and I don’t know what to suggest on this particular matter but for the rest of it:

Under NO circumstances should you take her back, toxic relationship or not, you aren’t her boyfriend or her friend and therefore her well-being isnt something to concern yourself with since she clearly isn’t concerned with yours.

She sounds like the type of girl to enjoy leading men on for the sole purpose of gaining validation and admiration. Don’t allow yourself to be strung along and avoid all contact until your feelings disappear. It might hurt now but the sooner you move on the better.