Hi Patrick,
When you say she has milk, how do you mean - have you checked all her teats? Does the teat take a bit of squeezing to get the milk, or does the milk squirt out from a gently tug?
They normally start to get milk in the fron nipples and slowly work back as the sow gets closer to farrowing, at first it will take a bit of a squeeze to get at the milk but up to 24hrs before the birth it can be very easy to extract - with a gentle squeeze.