Dental Practice where private a NHS work carried out and Furlough

I had a tenant contact me as she has been furloughed. She has been told by her employer that her furlough income will solely be based upon the private patients side of the business.
She has to be on call for the NHS side for emergencies, so not furloughed from that. She will only be paid for the NHS work, if and when required.

She has yet to receive a payment from the employer, but she is not expecting it to be anywhere near 80% of her usual income.

I have not heard of anything like this and cannot find anything regarding this situation.

Anyone else had this situation arise.

The advice on this thread seems to indicate the furloughed money only equates to 80% of contracted hours so if NHS is on call and depends on what she does that could be problem unfortunately