Dear Brenton,
What your daughter is personally liable to pay back at law will depend on whether she is listed as a borrower on the loan agreements. If she and her husband are listed as joint borrowers on the bank loan then more than likely they will be jointly and severally liable to pay it back. So if one doesn't pay it back or cannot, they will go after the other person. Similarly, if the loan from his parents was in writing and names both of them as joint borrowers, then she would also be liable to pay it back.
However, if your daughter and her husband have agreed on a property settlement as outlined above - ie that she pay the $25,000 bank loan and he pays the $50,000 loan to his parents, then that will determine what she is to pay. If she failed to pay the bank loan for example, his name is still on it so the bank would come after both of them to pay it, so he is still liable to the bank at law. But he can produce the agreement to say that she agreed to pay his share of it to a court, which would then likely require your daughter to reimburse him for what he was required to pay to the bank.
It sounds as though her husband is being reasonable, so I would encourage her to finalise a complete property settlement involving ALL of their joint assets including real estate, cars, super etc and put it in writing as soon as possible. If you need help, see a lawyer - it is well worth the money for peace of mind and closure.