claiming esa when recieving employers sick pay

An ex nurse wrote: I am helping a friend who has just been diagnosed with cancer and is about to start chemo and radiotherapy. She has a full time job and will be recieving some sick pay from her employer and hopes to return to work following treatment , this is predicted to be next february. She has many years of full national contributions. Under these circumstances is she entitled to claim contribution based esa whilst recieving treatment and is there a qualifying period ? Many thanks