My daughter were diagnosed of nkt cell lymphoma. She has 6 cycles of chemo now she abcess gums for almost one mobth. Is it connected with lymphoma?

Needs to see dentist. Hard to tell without an exam by a dentist. Your daughter should see a dentist as soon as possible. Having an abscess during a time when she is undergoing chemo can have significant consequences as her immune system is compromised.
Maybe . Patients undergoing chemotherapy need to visit the dentist every three months as the teeth and jaw bone can suffer effects from chemo. Please have your daughter seen by a dentist to treat abcess because her immune system may not be as strong since she has undergone chemo. Dental abcess can be life threatening if untreated especially for patients undergoing chemotheraphy.
Side effects? It is possible that her gum problem may be due to the chemotherapy she was getting. Check your oncologist about possible side effects of medication.