Definitely go . have a good time. Just pretend she's not there
Go to the bbq , and be happy !let her see that your happy and smile at her , even though it bothers you that shes going to be there dont let her see that ! You'll be fine :)
Go to the BBQ and just ignore her. She can't bother you unless you let her, don't stop yourself from having a good time because your worried about someone else.