Sorry to hear that your friend's dying, but providing she can receive the care she needs at home, there's no reason why she shouldn't stay where she wants to be.
No one can force her to sell the house, but the children who want this are probably just thinking in terms of things being made easier for all concerned.
However, it's now thought that patients should be encouraged to remain at home if they feel happier there - and most do.
The house sale can't be forced. It's your friend's home, and she can remain there for as long as she wants.