Hallucinations after an occipital lobe stroke

Patient: My grandma recently had a stroke in her occipital lobe and since then has been experiencing hallucinations i.e thinking she has been kidnapped and held against her will, talking to people who are not there.The doctors eventually found an infection although they were unsure wether it was in her lungs or her liver but have treated it for five days with antibiotics. We thought the hallucinations had gone with it, however yesterday she told us about the train station on the next floor of the hospital and the dancing school who had their lesson on her ward (non of which was true).I am worried that this could be a long term effect from the stroke but the nurses seem to think its old age and dehydration. This worries me as neither her age nor hydration levels have not changed since before the stroke and before the symptoms. Could this be a product of the stroke and will it be treatable?