Feed for 5 month old fawn

At 5 months old she should be on full blown deer feed I would say, or whatever you are feeding your herd. No milk. Feed and water

Her digestive system is fully developed and she is able to process forage matter and feeds. She is able to eat the same as others are eating. Let her slowly get introduced to the feed and don't switch her from one product to another all at once . Over a two week period transition her from what your doing now into her new diet.