Hi J., your daughter is angry and jealous and she doesn't know how to express that verbally so she is acting out physically. You are right that you cannot leave her alone with the baby, even for a moment. My daughter was the same way when we brought her brother home. Three years later, she is still very jealous and picks on her brother when she's mad about something. At 22 months, you cannot reason with her. She can only see her side of things. Check out loveandlogic.com It is a very effective method of disciplining children and it even works on young children. Try coming up with one empathetic line to say to her each time she acts out, like "You're sad that Mommy's feeding the baby, I know that is hard for you..." follow it up with a hug, and just repeat, repeat, repeat. Do not let her see your anger or frustration. This can take awhile, but hopefully she will eventually know that you are empathetic to her feelings and that will give her back some of the security she had as your one and only. Good luck!