Waiting for the unknown is very frustrating

My Mother-in-law discovered blood in her urine in May and her family dr sent her to a kidney specialist. The kidney dr said she had some hormonal inbalance, but nothing out of the ordinary for 69 years; however, the dr noticed a spot on her liver and she was referred to a liver spec. That dr did a liver biopsy and on Aug 20th our world was turned upside down. After a PET scan, chest x-ray and MRI we were informed that my Mother-in-law has Stage IV lung cancer with mets to lymph, liver and 7 masses on the brain. Saw the Oncologist, Radiologist and Surgeon on Sept 8th where they determined that she needed to start steriods immediately for the swelling on the brain and radiation began 3 days later on the brain. She was also placed on Tarceva that same day and was told she could no longer drive, as they estimated she was 3-4 days from having a stroke. She has been given 6-9 months with treatment.
She did 10 applications of rad in a 2 week span and handled that pretty well. For the past 2 weeks we've noticed some memory loss, hand shakes, loss of footing/balance, mood swings, swelling of the fast and stomach, bad rash, voice and cough change.
My husband took her for a follow up apt yesterday and they went over all the signs to watch for given the lung and brain situation, but otherwise basically said we sit and wait for 8 weeks until they can do a follow up PET and MRI. Yes, she has another apt in 4 weeks to do a check up, but otherwise no treatment for 8 weeks. They said she can't drive for an undetermined amount of time.
We are very confused by all our emotions because this has happened all relative quickly and now we have to sit and wait for 8 weeks to know if the rad even worked. We're also very confused on why traditional chemo is not being offered. From what I read Tarceva is a maintenance pill typically used after traditional chemo. She hasn't had chemo yet and isn't being offered chemo. The dr's have just said that they can only hope that Tarceva helps to slow the growth.
Any advice or input would be greatly appreciated at this point.