Little annoying sister in law!!!

I got married two weeks ago and we had to stay with my husbands family because they're building our house. My husbands sister is 7 years old and she can talk all day, she's spoiled and talks back to EVERYONE. I get that she's a little girl but my in laws don't say anything and if my husband gets after her she's talk back to him, if I'm doing something on my phone or watching TV and she's talking I'll ask her to stop talking or not to talk so loud and she won't listen. I don't know how long I will be able to live with this every single day for the next year and a half. I'm in my first trimester and I can't take much of this! I want some peace and relaxation at least till my morning sickness, and fatigue calm down a bit. What should I do