Your bundle of joy is into parallel play. She will play alongside other children but not with them. Sharing, taking turns, cooperative play and being empathetic is an understanding that comes around 3 and a half years.
What you need to know
Presently, she cares about herself and her belongings more than others feelings. Show your child how you share things with your friend. May be sharing recipes, books etc. You can play simple games with your child. For instance, give her few flowers, cookies or blocks and ask her to give one to all family members.
Never force your child to share things with her friend. Initially, you need to respect her being possessive and accept her as she is. Watch how she behaves in a group. She may either be rejected by her playmates for not sharing things or will learn to say “No” when others don’t engage in co-operative play. Give her the time to understand and give her age appropriate guidance.