It doesn't matter if they mark it as a wheelchair or as a stroller, they are not allowed in lines. You'll need a proof of disability, go to guest services and there you'll get a card (either green or orange) and you'll be able to enter through the disabled entrance (the wheelchair/stroller is allowed there).
If you're a party of five, you don't need the exception, there can be 4 people, along with the disabled person, so 5 in total. But it you'd be with 6 people, sometimes the CM will make an exception, sometimes they won't
If you stay on side you'll book for the people needed (including their tickets), but you can send the proof of disability, if they deem she needs the help and you'll get a free ticket for one adult supervising, they'll return the money you paid too much. I don't have any experience with this myself, but I've heard of people who were successful with this route