can this happen and if so how long? Spoke to the vet and they said yes a week, What are your views on this

your vet prob said that as your girl may not have concieved on the day she was mated it can be up to 5 days later !!! i took one of mine for a scan when she was 30 days post mating and the scan showed the pups were only 25 days old ...so in theory she would have gone over by 5 days by her mating date........

Yes a week is possible but keep a close eye on her meanwhile.