Benign nocturnal leg cramps: This condition is common in older adults and can be caused by factors such as muscle fatigue, dehydration, or electrolyte imbalances. The long duration of symptoms (7 months) without mention of other severe symptoms makes this a plausible diagnosis.

Electrolyte imbalance (e.g., magnesium, potassium, or calcium deficiency): Electrolyte imbalances can cause muscle cramps, and deficiencies in these minerals are relatively common, especially in older adults with poor diets or certain medical conditions.
Medication side effects: Various medications, including diuretics, beta-agonists, and statins, can cause leg cramps as a side effect. Given the patient's age, she may be on multiple medications, increasing the likelihood of this cause.
Peripheral artery disease (PAD): Although PAD typically presents with intermittent claudication (pain in the legs during exercise), it could potentially cause cramping at rest in severe cases, especially if the patient has significant arterial disease.

Neurological disorders (e.g., peripheral neuropathy, amyotrophic lateral sclerosis): While less common, neurological conditions can cause muscle cramps. Peripheral neuropathy, for example, can result from diabetes, vitamin deficiencies, or alcohol abuse, and can cause painful cramps.
Deep vein thrombosis (DVT): Although DVT typically presents with swelling, redness, and warmth of the affected limb, in some cases, it can cause cramping without these classic signs. Missing a DVT could lead to potentially fatal pulmonary embolism.
Compartment syndrome: This is a serious condition resulting from increased pressure within a muscle compartment, which can cause pain, cramping, and potentially permanent damage if not promptly treated.

Sarcoidosis: A systemic disease that can affect multiple parts of the body, including the muscles, causing cramps among other symptoms.
Hypothyroidism: Severe, untreated hypothyroidism can lead to muscle cramps, among many other symptoms.
Muscle phosphofructokinase deficiency (Tarui's disease): A rare genetic disorder that affects the muscle's ability to break down glucose for energy, leading to cramps and weakness after exercise.