It might be much of an issue if she was born with it, that is, congenital. Also, if she's still young, it might impact her life much. But for an adult that is used to perceiving different smells, it might be tough to adjust just like in my own case. It will take a good effort to not slip into depression.
I think the first thing is to find out what might be the cause of her inability to smell. Then, you can take it up from there.
I am not sure why - I'd have to ask my Dad. She's passed now though. I think she was pretty tough - she went through war, migration, a difficult marriage, divorce and single parenthood.
I'm sorry to hear that.