Is the wife to be blamed for not returning the gold that the husband's mother gifted her in front of everyone, especially since she was not informed that the gift was temporary?

If the mother says that the gold is a loan and the wife says it is a gift, then the mother is not entitled to the gold unless she swears that it was a loan. This is because the statement of the giver is to be accepted, and this aligns with the principle: "If the recipient and the giver differ on the nature of the transaction, the statement of the giver is to be accepted."

It should also be reminded to the mother that retracting a gift is forbidden, as the Prophet (peace be upon him) said: «It is not permissible for a man to give a gift or grant a donation and then retract it, except for a father in what he gives to his child. The likeness of one who gives a gift and then retracts it is like a dog that eats, and when it is full, it vomits, and then returns to its vomit.»