Jealousy towards my daughter from my step daughter?

They are the same age. They are both female and the step has the disadvantage (at least she thinks so) of not being your biological child. Try to treat them equally. Try to do things with both girls where they have to cooperate instead of compete. Make sure the step knows you love her. Have you talked to the step and told her that just because she wasn't born from you, you still care for her just as much as the other daughter? When you ask your daughter about her day, try to rotate out questions with the step too. Or try waiting until both girls are home and ask about both of their days. She's just feeling insecure and a bit scared. But it sounds like the family relationship is good (she'd not be jealous if she didn't love you too). Try to make sure you hug and love on her just as much after your daughter gets home as before she did. She's wanting your child to see her getting attention too. Make sure she hears "I Love You" from you each day. One day she'll know its true and quit trying so hard. Right now she's just clinging to you and wanting a stable "mom" presence in her life. She's not trying to hurt your daughter, she's just trying to make sure that she's as loved and wanted as your daughter is. I know its hard being a stepparent, but its just as hard being a stepkid.