Based on my experience, I have learned to offer practical help, instead of asking the patient. If you ask them, "What can I do?" They're likely to say, "Nothing!"
When I first came home from hospital, I was relieved when a member of the congregation announced they had organised over a week's worth of suppers for us. Each evening, someone would rock up at the door with a hot meal. That saved Rob learning to cook at that point, and it saved me the stress of letting him try and not interfere!
As I mentioned before, just after I arrived from the hospital my younger son came home with a dental abscess. Again someone took him to the dentist for two visits in the same day. This sort of gesture was a huge help.
Depending on the schedule of treatment, your friend may need help with cooking, but also cleaning, laundry, changing baby's diapers, picking up the kids, etc., not to mention transport as time goes on.
I had a friend cut my toe-nails at a time when I couldn't reach them. The same friend washed my hair for me when I first came out of hospital. Transport to radiation was a problem for me. Most days, Rob could take me, but there were days he had other committments. I could drive myself there (45 minutes drive) but by the time the treatment was over, I was too exhausted. I would have been a hazard on the road.
If your friend needs a lot of help over a long period, consider creating a free web-based calendar, and advertise it amongst her other family and friends. People can sign up for the tasks they can help with and choose their dates as well.
So . . . keep your eyes open for ways you can help, and then say, "I'll come and . . . "