Living with lung cancer

The information above is for my 80 yr. old mother in law. She has recently been diagnosed with lung cancer, stage 4. She is taking Tarceva. She was hospitalized for 6 wks. She has been in convalescent care for about 2 weeks. She is doing physical therapy and can walk short distances. Not by herself though. She is under the impression that she will get stronger and be able to live by herself again.
Do you think this is an option or will the lung cancer continue to make her weaker and should we look for other care for her? She is also not eating well and has trouble eating (gag reflex).