low platelet count in my cat

My 13 yr. ol d cat was recently diagnosed with bi-lateral lymphoma in the kidneys.  She has had one chemo treatment so far consisting of one lomustine pill and a steoid injection.  Less than 1 week later, our local vet said the tumor had actually shrunk, however she developed an upper respiratory infection for c. 10 days, and then several days later, she vomited blood, had to stay overnight in the emergency clinic where she was given liquids and a blood transfusion, due to a low platelet count. That was 5 days ago.  
1. Is there anything that can be done to increase her platelet count?
2. Is it likely the chemo pill doage is too strong and is causing her to have a very low immune system? Would a lower dosage of the lomustine be recommended?  thank you for your input.