Stage 4 lung cancer - chemotherapy?

My mom has stage 4 squamous cell lung cancer with mets to nodes, adrenal and hip bones. Just finished one round of gem carbo chemo and seems to have less pain. However she now has a huge rash all over body. Is this likely from the meds? Will our oncologist make a change to her program? What is the likely period of time we can expect her to feel better from the chemo and what happens after that?