Just a quick update - over the last two days, my daughter has said that her hearing has gradually improved.
There has been no sudden pop where everything is suddenly OK, but she is hearing things at normal volume on the TV where she was struggling last week. She has been doing the exercises in the video that
@twosips posted, and I suspect that, along with time and a bit of breathing in steam, have all helped.
Thanks again to everybody who replied - Blue Moon is a great place for entertainment/footy/music discussion etc., but it's also a great place for practical help.