
At 54 days it is too early for puppies to survive, some bitches will show a clear mucus discharge some time in the last weeks of pregnancy, this becomes more noticeable before labour.
If there are not other signs of labour then I would not be concerned, but watch carefully.
As well as an experienced person to help does your sister have 'The Book of the Bitch' if not order it and it should arrive within 24 - 48 hours from Amazon, or you can get one in Pets At Home or similar. It needs reading from cover to cover and then the whelping parts while your sister waits.