Toddler jealous of baby

Hello, my 4 year old daughter is showing signs of Jealousy ever since our 7 month old baby girl was born. She scratches her, and pushes her forcefully down. She will say, "I'm a little baby again." She wants everything the baby has. In the passed she would bite her and hit her with things but when the baby cried in pain she said she didn't know that it was going to hurt her . But most of the time she will get into trouble to get attention. Both of her Grandmother's have told me she is doing it out of Jealousy. Also, when doing the mentor meeting with her she said her relationship with her sister is good, but sometimes its not because she wants to be with Mommy and Daddy. We are not sure how to handle this. I spend a lot of time with her all day and tell her I love her all the time. I would really appreciate your thoughts on this. Thank you.