Perhaps.

The IRS says:

"Medical expenses are the costs of diagnosis, cure, mitigation, treatment, or prevention of disease, and the costs for treatments affecting any part or function of the body. These expenses include payments for legal medical services rendered by physicians, surgeons, dentists, and other medical practitioners. They include the costs of equipment, supplies, and diagnostic devices needed for these purposes.

Medical care expenses must be primarily to alleviate or prevent a physical or mental defect or illness. They don't include expenses that are merely beneficial to general health, such as vitamins or a vacation." See IRS Publication 502.

Generally, this means that you need a doctor to state in writing that the chair lift was meant primarily to alleviate a physical condition such as arthritis or balance problems, such that her health and well-being required the chair lift.

In case of an audit, that is the documentation that you would need.