I was playing with my dog, and she was on her hind legs, then all of a sudden she started to wimper really badly and running away with her left hind leg clutched really tight.. i got a hold of her and then she calmed down, i put ice on it, but she still cant walk on it, is it sprained or broken?

How much would it be if i got an xray, or if it was broken or sprained. please help!!
shes a chihuahua, shes 7 pounds. she is holding it up, she isnt walking on it, when i move it she doesnt feel pain, she lies on her leg. is it broken or sprained?
she doesnt put it down, she just holds it up
I really want to take her to the vet, but my parents say shes ok. My mom is a nurse and she said we will observe her if she gets better then we wont take her, but if she isnt feeling better by mon we will take her she said.