My sister-in-law is suffering from meningioma, and has a vision problem. Is surgery the last option or can be cured by medicine?

No good Medicines he. Surgery is the best way to control/treat this type of tumor if it is causing any pressure symptoms, which will be size-related. How big is this tumor and has she been seen by a neurosurgeon? He/she can give you the best advice.
No medicine. the treatment is either localised radiation /surgery or just observation.