There are a couple injuries that could fit the description you relate. The best plan for now is to keep her quiet overnight and reassess the degree of use, whether there is any visible swelling and if the "pop" is still present. If you can provide me an update tomorrow I can guide you as to the best course. Almost any injury to a limb is repairable and most we would have at least 72 hours for optimum outcome. You can give aspirin at the rate of 5mg/pound body weight, you could give now and repeat at bedtime. Let me know if you have any questions and please give me an update tomorrow.