My grandma just slapped me on the shoulder and yelled at me for no reason!?!?!?!?

ok so we are moving and she told me to get my room packed up today, so i got box full, and remembered i had packed one yesterday that still needed to be packed. so i went into the living room and told her i had 2 boxes that needed to be taped, cuz she has the tape. then she came into my room and saw both of them and said, "wheres the other one?" i said, "they are right here" and pointed to them and she said "no, this one u packed yesterday, u are trying to make it look like u did more work then you really did." by now she was looking really mad, and i said, "yes i know i did that one yesterday, but it needs to be taped so i can move it and pack some more out of the closet." then she walked over to me, slapped me on the shoulder and shes in my face and she yelled, "you cant pull that bull s**t on me!!! i know your just being a lazy smart a*s, and i dont have to put up with it!!!!" then i said, "but gran-" but she cut me off and said, "NO!!!! i dont give a crap, dont lie to me!!!" by now i was shaking, i mean i was already convinced she hated me, but wow. so i just stood there, and she goes, "you lie to me all the time, i know you thing u get away with bull s**t like that, but i know it! so go cry to your parents i dont give a crap!" so i just stood there and she pushed past me, and she just glared at me, and for lack of anything better to do and not wanting to look into her eyes, i took a sip of my water to hide my eyes, b4 she slammed the door. so i just wiped my eyes so i could see and came straight here. not crying so much cuz she yelled at me, altho that is part of it, my shoulder hurts really bad!! she hit it with the palm of her hand right where it hurts the most. so what gives??!??!! why did she do that, and if i tell my parents, what do i say? they will just laff and say "im sure it wasn't that bad!!" and she will just sit there and laff. i have been wanting her out of my house for awhile now, but now its just over the top. i want her to go home, and get out of my house!!! she has an RV that shes been living in for the past couple of years, i want her to GO BACK!!!! how do i get my parents to believe me and her to move out?!? PLEASE HELP!! also does ice really work if i put it on my shoulder would it stop hurting?