Does a change on name on a lease make it a new contract?

Hi, I was just wondering if anyone could help me. My mother in law is currently renting a unit in NSW and has recently divorced from her husband who has since moved out. The husbands name was on the lease and hers was not. The dad is trying to find a new place to live but since his name is still tied up with the previous address he can't really do so. My mother in law asked her real estate what would happen if she were to change the name of the lease into her name and they have basically replied saying that she would need to repay the bond and it would be treated as a new contract. Now my question is, can they actually enforce this? My mother in law has been residing in the residence now for over 8 years it just seems a bit strange to me. Any assistance that anyone can provide me will be greatly appreciated. Thank you for your time.