Hmmm. Well it looks like Vesper and her love are caught in a cave fall in, which could be why the rest left without them. So the “time difference” has not changed for anyone. Vesper and friend are still trapped in the cave and in their own timeline, while Olwyn and the rest are back to their own time where 5 years have elapsed.
My view is not to make it more complicated than it is.
The big questions are: How will Winnie and Vesper get out of the cave? How will they get back to 1940’s Russia/Siberia and the rest of the Harker family?
If 5 years have past for Olwyn and company since they hopped into the portal and then back out again, is the war over?