#1) Get cat checked out by vet. Even a minor infection, in combination with the move, can encourage accidents.
#2) Treat mattress *thoroughly* with something like Feline Odor Neutralizer (F.O.N.). Cats have extremely sensitive noses and can smell where they went before. I would *pour* FON on the spots, making sure to saturate them, then put a fan on to dry the mattress. Any sheets, blankets, should be soaked in FON and allowed to sit in a plastic bag for 6 to 8 hours and then washed with liquid OxyClean and detergent. Washing in detergent alone is not enough.
#3) Purchase a mattress encasement to protect from future "accidents". Allerzip is a good one that you can get on Amazon.
#4) Change the litter box to something different, especially if it is an old litter box. Most cats prefer an open box to a closed one; an old closed litter box can become repellent to a cat. These WonderBox liners are great!
http://www.amazon.com/gp/product/B000MD3MDW
Put one in an inexpensive plastic litter pan from Walmart along with 3 inches of litter. Clean litter box every day, of course, and use a new liner and new litter every month. Helps keep the litter box attractive to the cat.
#5) Lock cat out of bedroom as much as possible.
#6) Watch cat while it is in the bedroom and, at any sign that she might pee, carry her to the new litter box.
#7) Get a Feliway plug-in to soothe the cat's nerves. These are available on Amazon and other places.
It helps to do *all* of these things simultaneously.