Many, many newborns get mild hiccups and we usually say, “It’s normal, don’t worry, it will go away soon”. On the other hand, if hiccups are very frequent, it is likely that something is in the breastmilk that doesn’t agree with her. Mom should avoid cow milk products first. If that doesn’t eliminate the hiccups, other likely culprits are:

Caffeine – coffee, tea, soda
Soy products
Peanuts
Shellfish
Chocolate (sorry!)
Citrus fruits
Wheat
Eggs

If the hiccups are still problematic after a few diet changes, then you should mention it to your doctor.