I'm guessing that she will give you the container when she gives you the starter. My dad made sour dough when he retired. He made so much he developed carpel tunnel, he made over 20 loaves a week. His was stored in a Rubbermaid plastic container. One that was square and flat like a 10 inch square pan with a lid. He said the flatness helped the dough gas off rather than a tall container. But it will probably depend upon the type of starter. Enjoy your new hobby.