Answer: Promissory estoppel
Explanation:
Promissory estoppel could be defined as a situation where a person can't go back on a promise even though there was no legal agreement between them. This was provided so people don't cheat on others and also the other party doesn't loose when they are in agreement with someone even when it's not signed in to law between them.
Jennie can recover her money under the doctrine of promissory estoppel if James doesn't wants to pay back.