I dont consider mine overdue until they have gone over 63 days from last mating and then i dont worry unless there is any signs of trouble. Last year one of my girls went 3 days overdue from last mating and she had 12 with no whelping problems at all.
Depends whether she is 3 days overdue from her last mating or 3 days from her first. If shes 3 days from her last one, she may actually be over 3 days late, if the first mating took. I would get her checked either way, won't do any harm and it will set your mind at rest.
so u only had the 1 mating ! so 2day is 4days over ? is she showing any signs at all ? are u taking her temp ? has she been sick ? has she gone off her food? is she nesting at all ?