Honestly, if you don't even have a bill of sale, stop calling her. She can take the horse back without you having any hard evidence saying you bought the horse legally. I know it sucks, but consider this a lesson learned and make sure to get a bill of sale with everything outlined, and a PPE.
You said you don't have a contract. Does that also mean you don't have a bill of sale? Without one, the horse isn't yours, it's still hers. I would continue to try to contact her. Good luck.
