Well can be not sure how GA ability is set but
if its an instancing you can directly access
However other ways to do it. You can just have a gameplay effect and a tag over target and wait for tag to be removed also can solve your problems.
Let me know if I am understanding your problem right.
I had a similar one for multiple attack type from enemy but I generally bind event to character itself not GA or you can add GA but pass variable as owner to make distinction between events of different instances.
