A worker has a disability. There are various adjustments you could make, all of them "reasonable". It would be preferable, as the employer, in terms of cost and business impact to do all of this at another location. The "new" location is no further from the worker's home, her son's school or her GP - and she has a mobility clause in her contract that you have relied on before. So that looks ok.
Until she claims that you could and should have made the changes without moving her to the new location and failing to do so is a breach of your obligation to her.
Location, location, location. The big question in the Employment Appeal Tribunal.