Normal or not normal toddler behaviour??

My 21 month old smacks other children not hard but pushes them away and will NOT share all the time,

Is this usually normal? Or this is a concern?? She talks very well for her age but some things she can't express. She hasn't mixed with a lot of other children tbh but when she does she kind of doesn't know how to share??

Should I be worried??? She will cuddle children then push them, then give them something and then take it away etc....c