Help!!

Hi everyone, I’m trying to help my mom with a PayPal problem. Someone sent her money for a product, and she didn’t put the money into her PayPal wallet, and now she cannot access that money anymore. The lady who sent her the money has now opened a dispute against her, but put that she didn’t receive the item. The lady who sent her the money has now opened a dispute against her, but put that she didn’t receive the item as she doesn’t really understand PayPal either. PayPal has now given my mum until 17 March to either refund her herself or prove that she has shipped the item. Obviously my mum can’t do either of these as she didn’t receive the money in the first place is there any way to resolve this easily? Thank you in advance❤️