Both you and the sister have to serve the same time. There is no ban lift for one and not the other. I would assume you both were banned under the same ip when she was banned earlier, so how you got unbanned is a mystery unless Arkham lifted yours with no warning (unlikely). The other two times the bans were not lifted and you waited the month as usual, this time is no different imo. Please wait until your sister’s account deletes as you did the other two times.