If Brienne is participating in a challenge can I activate parting blow. I guess my real question is: When does her effect wear off son I can start playing events again?

Edit: Sorry meant Brienne of Tarth. My auto word correct messed up the spelling lol.

She is participating in the challenge until all responses to challenge resolution have been resolved (and moribund cards have left play). So no responses, including Parting Blow.