Right rear possible coxofemoral joint luxation or fracture and they gave me some medication called buprenex does this mean her leg is broken?

Buprenex is a pain medication, it doesn't indicate whether your dog has a broken leg. There could be muscle damage, bruising, torn ligament, fracture, the list goes on, your vet would have just prescribed that because the dog was in pain.

Did they not do an x-ray?

coxofemoral= hind leg

joint luxation = dislocated joint

fracture = broken

Coxofemoral luxation is essentially dislocation of the hip. Basically the hip is a ball and socket joint - the head of the femur (the ball) has popped out of the socket (the hip joint).

If it is a fracture, it most likely means the ball of the femur has snapped off. This happened to my cat as a result of trauma and required surgical repair.

They didn't take x-rays?

You should ask your vet to explain her situation more. Hope she is all right.