With all the bad news on TV news shows, a story like this is quite uplifting. She managed to keep herself afloat for 10 hours before being rescued by a coast guard vessel.
I looked up the sea temperature and at the moment many parts of Croatia report a sea temp. of 27 plus degrees. She looks very fit and does yoga so this would have helped.
If she had been doing this cruise in mid winter she'd almost certainly be dead.
https://www.theguardian.com/world/2018/aug/19/british-woman-rescued-10-hours-adriatic-sea-cruise-ship-fall