Behavior problem?

I hope I can get honest and helpful opinions po pls. My daughter is 3y3m old. She is really sweet and can converse well with adults and her friends. However, napapansin ko nung nag 3yo sya parang nagiiba attitude nya. Naging madamot sya, she doesnt like sharing her toys with my sister's baby, grabe sya mag tantrums at mag make face, nandidila at naninipa sya pag nagagalit sya. Pls help me. Idk what to do and how to deal with her. Sa sobrang stressed at inis ko sa kanya nasisigawan at napapalo ko sya. Yun kaya yung nagpapalala ng attitude nya? She also doesnt listen pag sinasaway sya. She knows it's bad but she will still do it para magkulit or mang inis. #pleasehelp #firsttimemom