4 year old jealous of new sibling?

I had a similar thing with my 2 year old going from 1-2 was hard 😔 I realized it was because I didn't have as much time for her. I was still the one that would take care of her basic needs (changing, feeding ect.) But I also ebf and she went from being the single most important person in my life to having to wait. I would make time to do the things I HAD to do but wasn't giving her the love and attention she needed so she turned to dad, I felt horrible. I was about 3/4 months pp when I realized what was happening and took extra steps to make time for her. I remember one of the first times, I finally got baby to sleep so I put some music on and started jumping about dancing with her then she picked up a ball so we started rolling the ball to each other. Baby was cluster feeding and didn't sleep for long when he started crying her little face broke my heart she looked like she was about to cry because she knew I had to go see to him.

I started trying to include her more with baby. Changing him and playing with him and when I was breastfeeding I would get a game or something that we could sit down and play with one hand and she went from not going near the baby and preferring dad to being a mummy's girl again, cuddling into us while baby was feeding and constantly asking to hold her brother.