I have a 4 year old daughter who is recently acting out. she has become rude and very naughty and is always playing rough with her little brother who is 8 months old and the scary part now is she plays in ways that she wants to kill her brother.

Consult time: This is neither rare or acceptable behavior. I would ask your primary for a referral to a child behavior therapist for individual & family evaluation.In the short term the 4 yo should not be left alone with the infant. The 4 yo likely feels dethroned from a position of dominance in the family for the year plus you had to spend extra time in both maintenance & play with the baby. This can be fixed