I know a similar case as yours, except that the old lady has another daughter in China.
Tried 3 times for the first visa,
extended in US from 6 mon to 1 year,
went back to China and stayed for more than 1 year,
tried 2 times for snd visa.
Tried 3 times for the first visa,
extended in US from 6 mon to 1 year,
went back to China and stayed for more than 1 year,
tried 2 times for snd visa.