Thank you for your email. For some children being the middle child is not easy.
Each child usually has an identity within the family. The "oldest child" or the "baby of the family." The middle child however, sometimes struggles to find their place within the family.
You can help your daughter develop her own identity by focusing on discovering her unique talents and helping her develop them. Spend quality one on one time with each child but especially your middle child. Take her out for a milkshake and give her your undivided attention. Find opportunities to praise her and avoid comparing your children.
When you get home from work focus on your middle child ensuring you give her attention. Praise her for what she did during the day and show her you value her thoughts and opinion. When you do ask her to do something do it in such a way that she feels important. How do you think we should set the table tonight? Would you like to help me? Maybe you could decorate the table with the serviettes. Doing this will make her feel valued.
It may also be a good idea to give each child their special day so for example Monday is the oldest child's day, Tuesday is the middle child's day, and Wednesday is the youngest child's day. On those days they get to choose what food to eat for dinner. Have first choice, and are made to feel important by all family members.
Spend ten minutes before she goes to bed holding her on your lap and telling her how special she is to you and how much you love her. This is a good thing to do with all your children and will only take half an hour of your time with three children.
Good luck and let me know how you all are doing.