What medication can you give a dog for her period?

You might want to ask a vet but from what i know there isn't any how ever there are things you can do for your dog. such as

Give her a Massage, Especially in the hip area where she may be bloated

Let her Sleep most of the day but not all day.

Take her out for walks but with a doggy dipper. but keep other dogs away from her

Keep other animals away from her, Because she feels uncomfortable she will be very moody.

You also may consider doing something special for your dog. Something sweet and creamy will do the trick like plane yogurt or homemade Ice cream made with lactose free milk, or just the lactose free milk