How can I be happy when I'm around negative people?

My mom went to Japan because my grandpa just had a surgery for stomach cancer. Normally, she would have taken me but my dad wouldn't let her because of the mess in Japan. They argued about it, and when she told him that he should ask me if I want to go, then he says he doesn't care about my feelings and that he won't let me go no matter what. Finally, she had to leave me here with my dad. He promised to take me to summer camp and to places I wanted to go.

Now my mom is gone, I feel VERY lonely, depressed, and bored. I'm the type of person who gets agitated without my mom. (I'm 12 years old) My dad only takes me to his shop, and there's nothing to do except play computer games. And my grandma comes over too. She is VERY VERY negative. She complains about everything and only eats food. My mom SPECIFICALLY told my dad not to have her near me, and he agreed. Today, she was telling me that I should eat Korean food, not any other food, and that I should visit my cousins from my dad's side, and also move to Korea. (She is Korean.) She was also complaining about my mom. She keeps on saying like how selfish she is and how she gave me this and that. I always try to ignore, but I can't. Can you people tell me how to ignore someone? She also keeps on saying how she misses my other cousins. Like Hell-O? You missed me too! I also have a feeling that she dislikes the Japanese. I mean, she speaks Japanese, my mom's Japanese, and I'm a little bit Japanese too. Yesterday, she started to complain why the Koreans are helping the Japanese with the Nuclear disaster. Today, she started to talk proudly that since the Japanese fell, the Korean business is going great. If I had the guts, I would of probably told her to shut up. But I don't.

It's been only a day since she left. It feels like it'll take a LONG time until a month and 2-3 weeks is up. I feel like after a week or two, I'll go crazy. I also feel scared of everything. During the day, I feel happy and fine. At night, I feel afraid of everything, like 2012 (I don't think it'll happen...), or like some Alice in Wonderland game picture I found on the internet. There was a goth looking Alice holding a knife and next to her was a deranged, zombie-looking Cheshire Cat. I couldn't even sleep and was crying like crazy yesterday. So I slept with my dad. I can sleep with him, but not always because he doesn't want the sleeping with a parent to become a habit.

I feel miserable with all the negativity, loneliness, and such. Even if I tell my mom how miserable I am, she will say "Keep waiting, I'll come back soon." Can you PLEASE HELP ME!?!?!?!?!