Tarceva question

Hi, my mom has Lung cancer NSC stage wet III B and has been received 1 cycle of chemo which was 6 chemo and 3 weeks each.The first two chemo did not work but has been working since the thrid one work but stopped working at last so her doctor suggested her to start on Tarceva with 100mg and start Tarceva 150 mg one month after. My mom has taken tarceva for almost two weeks, she has rash on her faces and has been suffering from Diarrhea. However, on these two days, she started to cough again and the pain on her back comes back. I am wondering if anyone knows if this is normal for her and how long will Tarceva normally start to work? Please help. Thanks!! Louis