To assess the patient, a comprehensive approach would be taken, including:

A thorough medical history to identify any pre-existing conditions or medications that could contribute to the symptoms.
A physical examination to evaluate the patient's mobility and overall health.
A cognitive assessment, such as the Mini-Mental State Examination (MMSE), to evaluate memory, attention, and other cognitive functions.
Laboratory tests to rule out reversible causes of dementia, such as vitamin B12 deficiency or thyroid disorders.
Imaging studies, like MRI or CT scans, to evaluate for structural changes in the brain.

Alzheimer's Disease: Given the gradual decline in memory and physical mobility over the past year, Alzheimer's disease is a strong consideration. It is the most common cause of dementia among older adults, characterized by progressive cognitive decline.

Vascular Dementia: This is the second most common cause of dementia and can present with similar symptoms to Alzheimer's, especially if the patient has a history of stroke or vascular disease.
Mixed Dementia: Many patients have a combination of Alzheimer's disease and vascular dementia, which can make diagnosis and treatment more complex.

Normal Pressure Hydrocephalus (NPH): Although less common, NPH can cause dementia, gait disturbance, and urinary incontinence. It is treatable with the placement of a shunt, making it a critical diagnosis not to miss.
Hypothyroidism: Severe, untreated hypothyroidism can cause cognitive decline and dementia-like symptoms, which are reversible with thyroid hormone replacement therapy.
Vitamin B12 Deficiency: A deficiency in vitamin B12 can lead to neurological symptoms, including dementia, which can be reversed with supplementation.

Frontotemporal Dementia: A group of diseases characterized by the progressive degeneration of the frontal and/or temporal lobes of the brain, leading to significant changes in personality, behavior, and language.
Creutzfeldt-Jakob Disease: A rare, degenerative, fatal brain disorder that leads to dementia and other neurological problems, though it progresses much more rapidly than Alzheimer's disease.
Chronic Subdural Hematoma: More common in the elderly after minor trauma, it can cause gradual cognitive decline and is treatable with surgical intervention.

The initial treatment plan would focus on:

Diagnostic Clarification: Further testing and evaluation to confirm the diagnosis.
Supportive Care: Providing support to the patient and her family, including education on the disease process and available resources.
Safety Assessment: Evaluating the patient's living situation to ensure it is safe and supportive of her needs.
Medication Review: Reviewing the patient's medications to minimize polypharmacy and potential drug interactions that could exacerbate symptoms.
Referral to Specialists: Referring the patient to neurology, geriatrics, or other specialists as needed for further evaluation and management.
Cognitive and Physical Therapy: Considering therapies to help maintain cognitive function and physical mobility.