Is there anyway she can switch to a PC / laptop it might bring better results. Below is how to proceed on those devices ask mum to try this on her tablet, might work there too.
Click on Payments >> Summary then any payout available for immediate withdrawal, is available for you, in a big blue banner.
Click on that Withdraw > arrow, you may need to log in again, or even verify your account by receiving a text or email code.
On the pop up screen which appears, click on Withdraw found at the bottom of that screen. You will see £0.00 at the bottom, at the top a larger £0. There, manually enter the amount you wish to withdraw. Bottom right click on > Withdraw.
@mardye_933