Mango Cancelled Flight Costs ME R2000.00 EXTRA

I am HIGHLY disappointed in Mango Airlines!! A family member of mine is coming to South Africa from Ireland, she is travelling from Dublin-Durban & then need's to get on a flight from DBN-Cape Town that very evening (20th of September). I purchased her flight in APRIL, she was set to leave Durban at 7:30pm (Her international flight is landing at 4:30pm). We received an email TODAY, 10 days prior to her flying, that Mango has changed her flight to 5:30pm on the 20th. I called Mango immediately to which I was told the 7:30pm flight had been cancelled for the day & the 5:30pm flight was the last one leaving for the day but I was entitled to a full refund for my flight should I choose to cancel it. I HAVE NO CHOICE! My family member will NOT make the 5:30pm flight on the 20th as she is only landing at 4:30pm. Upon looking for a new flight & due to it being ONLY 10 days prior to when she is due to fly & a long weekend, the only flight we can find is going to cost R 4500.00 +!!! I paid R 2555.00 for the Mango flight, which means I am now paying ad additional R 2000.00 because Mango decided to cancel the flight. This is completely unacceptable, in order to compensate for the extra cost I am now going to have to incur; I expect Mango to reimburse me for the additional cost of R 2000.00 I am now going to have to fork out in order to re-book her flight with an alternative airline. She is unable to fly out any other time other than the evening of the 20th as she has a commitment on the morning of the 21st. I expect feedback & action soonest.