Mother just diagnosed with nhl diffuse large b cell w/ high proliferative rate

Concerned daughter. All advice is appreciated. My mother is 51 yrs old. She went to the dr around the first of November. She went to primary dr because she noticed a knot on the rt side of her neck that seemed to come up over night. They gave her antibiotics and told her to come back in 10 days if it wasn't better. Needless to say she was then sent to a eye, ear, nose, & throat dr. The first attempt to get a biospy was not sucessful. (fine needle) She then had a biopsy done on November 16. The dr took out some of the mass but some is still there. She was sent to the oncologist who then confirmed she does have nhl diffuse large b cell w/ a high proliferative rate. She had her first round of chemo on December 5 of rituxin and two days later CHOP. On Monday she received the Neulasta injection which was this past Monday. She has had a terrible cough for over a month. She also has spells of dizziness and what she says as everything goes black. The drs keep sending us back and forth and I feel like the issue is not being addressed. Has anyone had any syptoms like this? My mother is on a cough suppressant and it is not phasing the cough. She has not had hardly any sleep because she feels like every breath she has to cough.