Help please???????? i don't know what to do :(?

Please help. My cousin is in danger I think. I went over to her house to go swimming with her brother, because he is my age. She is my older cousin and was working (they have a ranch and she was feeding horses i think.) Then she started cleaning her Dad's truck. She asked me if she could use my phone to call her mom. See she wants her mom to come pick her up. One day her dad and her stepmom went to go eat and she wanted to go. her dad said no and she kept saying how she wanted to go. then her stepmom told her to quit whining like a little baby. she said i'm not and her dad told both of them to shut up. when they left she was really mad and punched the wall,but she didn't mean to make a hole in it. so her little brother helped her make up a story that she was playing with their dog and threw her toy but it accidently hit the wall. then her dad came in later on with a hot shot (a thing to brand animals like steers) and said that if he found out that she punched the hole in the wall he would beat her until she couldn't walk. her mom recorded her saying that while they were on the phone and i am really scared for her. her mom said that she is going to show the recording to the police. my mom works with stuff like this and before she used my phone she asked what time my mom got home. after you answer this please dont tell anybody. my cousin will get in serious trouble and i might never see her again. what should i do? her mom said if anything does happen to come to my house and call her. should i tell anybody? what do i say to comfort her? please help. i dont want to spread rumors in my family because if her parents find out then she will get in serious trouble. :( what do i do? :(