Hopesprings, they want to get her off the ventilator because the longer one is on it, the harder it is to wean from it. For her to speak with the tracheostomy, she would need some training in how to do so. Essentially, she would have to cover the hole in her throat when she speaks. Her voice would sound the same, though maybe a little hoarse at first from the vent tube. Patients with a trach have to be suctioned regularly as mucus collects. They can also develop a mucus plug which cuts off oxygen and is potentially fatal. A family member can be taught to do the suctioning, but in the beginning they will probably have a visiting nurse do it. There is also risk of infection.
The best case scenario would be for her to be able to get off the vent before going home and being able to breathe on her own. If that fails and it's the only thing keeping her in the hospital, they will likely want to do the tracheostomy.
Hope this helps a little.
Hugs,
Connie