It depends how big it needs to be. You can get a folded wheelchair into the centre of a Honda Jazz or the larger Honda Civic because the rear seat squabs fold upwards and that would still leave space for a dog in the load area. But, of course you would then only be able to carry one passenger, in the front. If she needs something altogether more spacious: a Citroen Berlingo Multispace, a Peugeot Partner Combi, a Volkswagen Caddy Maxi Life, or Renault Kangoo Combi that now comes in three lengths.