Dogs who don't know how to play just need encouragement and the right toys. I would start by buying a Kong type of toy that you can stuff with her dry food along with peanut butter. As she nibbles on the food she will get used to the smell of the rubber and/or plastic. Here are some of the best kinds of toys to use: Toys
. You can also pick them up at most pet department stores. Instead of feeding her a meal, just put all her food in the toys dispersed throughout the day.
After she is used to those toys, you can try a tennis ball. Have an adult put a little slit in the ball and put a few treats in it. As soon as your dog learns there are goodies in the ball, she will start bringing it you, at which time you will give her some of the treats. Then throw the ball. She'll bring it back to your for more cookies.
Most importantly, expose her to these toys gently and with lots of reward and praise and I think she will come around. Keep in mind that all dogs do not necessarily like to play and she might be more into walking, running, swimming, agility, flyball, obedience training. In fact obedience training would be a great thing to do to bond better with her and to work on her socialization. I highly recommend it for this dog. Good luck!