She is lucky to have found you! My first word of advice is to get another goose to keep her company. They are flock animals and like to be with others. We had one goose when I was young and she was so lonely. She used to watch us through the French windows and peck at the glass. In the end, we gave her to a friend who had a small group of geese and kept them as pets. She was much happier with them. Other than that they need enough clean water to immerse their heads, suitable food (grass or specific food for geese), a secure, clean, dry and draught/rat proof place to sleep. They are on the delicate side so if she seems lethargic, wobbly on her legs, etc, get her straight to the vet - don't 'wait and see'. Also, get a 'how to care for geese' book and have a good read. They are lovely birds, very loving and sociable. They also live a long time so you should have your friend for many years to come.