I’m currently exclusively pumping for my daughter so I’m aware of this. Fortunately I’m an overproducer and have a freezer drawer full of frozen milk. However, since she is specifically nursing, how does she start the process? If she pumps between feedings it will take a while to increase her supply. There are no breast milk substitutes, and the father is being a douche for denying his daughter proper nutrition.
after baby is done eating, she should pump immediately...getting as much as she can even if only an ounce or two. Each time she feeds she should continue to do this adding to each little amount until she starts producing more at every feeding. It is a workable option, it will just take a little bit of time to get enough for his first weekend.
Revenge is more important than his child.
In the animal kingdom it's frequently not the father that protects the baby. It's the mother. Same among humans.