Stroke: Given the history of a coiled brain aneurysm and sudden onset of symptoms, a stroke is a highly plausible diagnosis. The absence of pain does not rule out a stroke, as not all strokes present with pain. The patient's age and history of diabetes also increase her risk for stroke.

Diabetic Neuropathy: Diabetes can cause neuropathy, which may lead to numbness or loss of sensation. However, the sudden onset in this case makes it less likely compared to a vascular event.
Seizure: A seizure could potentially cause a sudden change in sensation or awareness without pain, especially in someone with a history of brain aneurysm.
Transient Ischemic Attack (TIA): Often referred to as a "mini-stroke," a TIA doesn't cause permanent damage but is a warning sign of a future stroke. It could present with sudden neurological deficits without pain.

Subarachnoid Hemorrhage or Re-bleed of the Coiled Aneurysm: Although the aneurysm is coiled, there is still a risk of re-bleed. This condition is life-threatening and requires immediate medical attention.
Spinal Cord Infarction: This is a rare but serious condition that could present with sudden loss of sensation or motor function without pain.
Meningitis or Encephalitis: Infections of the brain or meninges can present with a wide range of symptoms, including sudden changes in neurological status without pain.

Conversion Disorder: A psychological condition where a person experiences neurological symptoms without a clear medical cause. This would be an unlikely diagnosis given the patient's medical history but should be considered if other diagnoses are ruled out.
Multiple Sclerosis or Acute Demyelinating Neuropathy: These conditions can cause sudden neurological deficits but are less likely in an 85-year-old without a prior history of such conditions.
Vasculitis: Inflammation of the blood vessels can cause a variety of neurological symptoms. It is rare and would be considered if other diagnoses are excluded.