Hello everyone! Are your kids also too jealous?

Hello everyone! Are your kids also too jealous? Mostly in our age group. My daughter is very selfish, wants everything to be only hers. Will it pass with time? Maybe there's such a period? For example, my husband's sister-in-law (4 years old) plays some toy, then my daughter immediately takes it away with a tantrum. How can I teach her not to be selfish? I explained it to her but seems like she doesn't understand ? I attached a photo