Is your boyfriends mum in pallative care being monitored for her pain they wont let her suffer if pain gets too bad she prob be given morphine its hard when they decide not to continue with treatment but maybe she just wants to make the best of what time she has left i watched my dad die just over year ago with lung cancer and its hard your boyfriend just needs time he knows ur there for him and he will need you when the time comes he prob feels he has to stay strong for her all you can do is love him and support him its horrible disease and horrible to watch and for his mums sake hope she has peaceful ending theres no easy answer sorry but ur not alone ule get support from cancèr support team  it was marie curie who gave us help hope this helps little