"3rd degree" just means full thickness burns. She was an older woman, thus had thinner skin; the spill was onto clothing; the spill was into a seat where she had limited mobility.

But ignoring all of that: hot water is dangerous and can cause full thickness burns in seconds.

http://www.accuratebuilding.com/services/legal/charts/hot_wa...

At 60 C you'd have full thickness burns in 5 seconds.