Bikes for that weight exist, but they come with the price tag of a really good bike. I am not sure that any one that has allowed their physical fitness level to suside to the point that they weight that much is going to want to spend that kind of cash on a bike that is strong enough to do the trick. Again, no offence intended, but spending that kind of cash on a bike implies a love for the sport. No one that weighs 360 pounds "loves" to bike.

Perhaps some other form of low impact exersize until her weigh has come down enough to realistically afford a bike would be better. Make the bike a prize for loosing some pounds.