My guess is that your well-adjusted daughter will go through all the normal responses of any child who now has to share her parent with another child. Your daughter certainly should be told about your intentions to adopt, in a manner appropriate for her stage of development. Any reputable adoption agency should be able to provide you with advice and resources to help you present this information to your daughter. I would also recommend that you ask the adoption agency for the names of other adoptive parents who have adopted two or more children. They might provide the best resources for you both before and after you adopt your second child. I wish you well.
Adopting a Second Child
Toddler and Teenager Expert Advice from Carleton Kendrick, Ed.M., LCSW