So sorry to hear about the issues your mom is seeing with this! That sounds very uncomfortable to say the least. Fungal infections can be tough to deal with- how's her diet and hygiene? If it's a fungus, make sure she is staying away from sugar and carbs- the infection can 'feed' on those and makes it worse. Also, make sure she is keeping very clean- changing socks regularly, using clean towels every time- washing all sheets and clothing is hot water. You can use vinegar in the rinse cycle of the laundry- and you can also use a mix of vinegar and water to clean the infected areas.
It is certainly possible it's also not a fungus causing it, so if those steps don't help (in combination with the medication from the doctor)- make sure you follow up and push them for other answers.