If you are just helping the way you say I don't think it's required. It is more for once the app is submitted if you want to be able to communicate on her behalf with IRCC. The rep would also get any correspondence regarding the app sent to them. In our situation I am appointed for my wife, she felt it would be easier for me because of a possible language barrier. we are together during the processing so probably wasn't really necessary but certainly won't hurt. Make your decision based on your situation.
