I am abit worried with the story.
The bank cannot just decline to payout without a valid reason as we have public and private liabilities linked to transactional fraud. My point is, the fraud that went off as a base. You stated the CC has a limit of R25k, but more than R40k went off the card? Thats not possible. Unless its two cards. Next. Did she file an affirdavit? Your mom reported it, but you actually need to fill out a form (essentially an affirdavit) for the transactions dates. You then have (i stand corrected) but I remember 21 Business days for investigation.
From an investigation perspective it becomes difficult at times, if it was via pin and code verification. Now you need to prove further whether these transactions are out of normal behaviour.
bank cant just decline a fraud claim. Its a process. Get the decline report and take it further. Request your statements on the card to ensure the transaction have indeed cleared, and request a report as to how R40+ cleared on a R25k limit?