Confusing~

Why? I am so confused.  My sister and my bf seem not to get along too well.  Well, i understand my sister is not an easy person to get along with because if she doesn't like someone, she doesn't like someone. There's no choice or something else that he/she can do about it.  She's too serious on everything.  On the other hand, my bf is the person who is so easy to get along with people.  But when they are together, the chemical is not working.  Sigh~ and i am in the middle.  I know my sister is rude sometimes, like if he says hi to her, she has no response or just try to avoid.  Isn't it rude?  Anyway, i can't do anything to help it.  There's so many misunderstanding between them. 

I think the reason is because of money.  She thinks he lives with me right now without contributing anything and it's my family's house.  Honestly, i don't know why she's so into money and she's sort of material.  But she's my sister, there's nothing i can change the relationship. Just let it be~