yes, she will probably have to sell. 1) she agreed to it in the diorce settlement 2) she presumably now has a court order to sell. If the kids are grown up, she could either get a job and use the 50k for a deposit to buy a place, or she could rent something. lets assume rent is 500 per month for a 1 bedroomed flat, she could rent for 8 years with 50k, so it's unlikely she'll be homeless.
you don't say if your friend just dosen't work or can't work, but how is she being supported now? will that carry on after the house is sold? Is she paying a mortgage now?