I'm doing a Fringe rewatch. In the episode where Altliv crosses over to the prime universe how did she open the portal when she wasn't a Cortexiphan recipient? I thought Olivia was necessary to open the portal then Walter's device and William Bell's sacrifice would hold the door open? It seems like all that was needed was the device and Bell's sacrifice, because Altliv shouldn't be able to jump like Olivia since she wasn't dosed with Cortexiphan. What did I miss?