Well, first of all...they have to find her to serve her. Tell her to not sweat it. They just want to get paid. They are not going to take her to court, that's just a scare tactic. It will go to a collections agency, then the agency will attempt to contact her to get payment. (The collection agency buys the debt, and then will come after your friend for payment.)
So lets say your friend owes $1,500....the collection agency will "buy" that debt from the payday loan company for pennies on the dollar...or probably around $400. They will then go to your friend and say, "pay us $600" (or however much they try to get) "and we wont put this on your credit."
It's not the worst situation, and they are just trying to scare you into paying. Stand tall against these loan sharks!