Its normal for toddlers to be possessive about everything. Encourage her when she makes an effort to let go of his possessiveness and share. Lead by example. Have friends over to spend time with you all so she learns through observation that “the more the merrier”. Be patient with her. Once she starts to feel secure with the idea of sharing, the possessiveness would slowly melt away. With time, kids also often learn that sharing is a reciprocal process and that they need to share with others if they expect the same in return.