When my soul sister was diagnosed last year these are the things I did to help her:

Be an ear on the phone when she needed it, went over when she needed me to (even for 10 mins)
Help her to get into a positive mindset, also helped her with her diet, looking at foods that would help boost her system etc
Food, especially for nights after she had radiation/chemo.
Yes helping with cleaning etc is brilliant, if she has a porta-cath put in, she will have problems moving her arm for a few weeks after it is put in & restricted movement for some time afterwards
Take her to the hairdresser to get a really funky short cut, it is less stressing if they lose short hair than long hair.

Prayers on their way.