Expected to pay penalties for flight changes that are required by the airline

My son's girlfriend was due to fly home on 29 December. Her travel agent told her on Monday 28 December that the policy had changed and she now needed a COVID test to board. We heard that testing at OR Tambo took 4 to 6 hours, so paid penalties and changed her Kulula flight to earlier to accommodate the test Unfortunately the information was wrong and the test would not be ready in time, so she changed her Ethiopian flight to the next day, and booked into a hotel (R1800). Unfortunately her test was Positive so she could not fly and came to quarantine with us. She quarantined, but was expected to test negative before being allowed to fly, so, 3 more tests later, each at R850 a test, she finally tested negative and could fly. However because she had already changed her flight once, she was now expected to pay a penalty of USD300. This feels to me like bad practise, especially considering the fact that the warning she was given about the test was the cause of a lot of extra costs and also due to the fact that she could not fly because Ethiopian Airlines would not let her. How is this her fault? I believe she should be refunded the USD300.