Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with a doctor.
Without the ability to examine and obtain a history, I can not tell you what the exact cause of the symptoms is. However I will try to provide you with some useful information.
Treatment of lymphoma includes a combination of chemotherapy. Some of these agents are neurotoxic in that they can adversely affect the nervous system. For example, vincristine, a medicine for lymphoma, can cause a sensory/motor neuropathy. Additionally, the lymphoma itself can affect the peripheral nerve causing various neuropathies that can include the cranial nerves.
I would recommend that your sister follow up with her oncologist for further management, workup, and diagnosis.
Thank you for this opportunity to answer your questions, I hope you find the information I have provided useful, good luck.
thank you for the help with my short information was given