Why is my 7 year old cousin having fits like a 4 year old HELP!?

i have an 7 year old cousin she always cries and has a fit when it doesn't go her way.. and it gets me in trouble im 14 and she is 7 so there is a big age difference between us. Im maturing and she still has a long way to go.. but anyway she hates chocolate and chocolate cake and since yesterday was thanksgiving and my aunts birthday is on the same week but not on the same days so my grandma bought a chocolate cake because its her fave flavor of cake when she saw it she had a fit and started crying like a 2 year old and since my brother and i are the oldest grand kids we are kinda forced to play with my lil cousins. so i said ok sure. and she starts crying to my aunt saying emilie wont play with me she hates me and ur just waiting for alexis ( my cousin that's the same age as me) and the reason why i wait for my cousin alexis to come to my grandmas is because me and her are the same age and we like to talk and about like teenage stuff and i never see her at all i see my 7 year old cousin all the time and so she doesn't understand. than later that night i said anna starts having a fit because she said i mean things when i didn't say ****! and my dad yells at me for no reason.... then i told my mom what really happened and she is like iknw emilie your not in trouble... and my family calls her the drama queen because she starts all this **** to get me and my older cousins in trouble than i tell the Truth and then they get in trouble for lying but why does act like such a drama queen for no freaking reason and it pisses me and my cousins off because we dont do **** help!!!