I am sorry to hear what has been happening to your mom.
Your mom cannot force her way into the property unfortunately, if she were to do this she would run afoul of the law. What she may do is commence legal action against him for the return of the property and/or the cost of replacing it.
Usually, once there is the threat of legal action, persons are usually more accommodating. What I recommend therefore is for her to write to him advising of her intention to commence legal action for the return of her property. With respect to the money, she may just have to commence legal action to have this returned. She is first required to write a letter to him asking for it to be returned. She is required to give him some time to comply, usually 14 days. If he fails to repay in that time, she may issue a claim in the small claims court.
Here is where she may file the claim.
Can I clarify anything for you? I hope I have answered your query in a way that is simple and easy to understand. If anything remains unclear, I will be more than happy to clarify it for you. In the meantime, thank you once again for using our services.