She is confused by the fact that she's in love with her brother. In our society that's not something normal. She's not confused about her feelings she's confused about her situation. Simon was quite on the right track actually. I understand that some people might not like her anymore because she's not the usual anime younger sister that sees her brother like a God. This is a normal family that go through a strange phase. It's normal for them to be confused about the whole situation.
Tris is teasing him because that's what she was doing for 18 years. That's their relationship. She's the spoiled younger sister and she got used to have things her own way. Because let's face it, in most situations if there is a boy and a younger sister in a family, usually the girl is the princess of the family. The older brother has to take care of her, he becomes the younger parent even if he wants or not. The fact that she teases him it's because she knows she can. Maybe she did that when they were younger. She saw that the toy cars of his brother were more shiny so she wanted them. To avoid conflict the parents told him "Come on, you're the older brother you understand... And so on.". Yeah she's a bit spoiled, but she was spoiled from the beginning of the game, it's just that people misinterpreted the situation. The phone scene in the first episode. She was behaving like a queen in the car, yet nobody said a thing to her. It was clearly her fault, yet they both took the blame. And even if she's a bit spoiled, and her daddy princess she's still a normal girl, who likes a boy, but that boy in her case is her brother, which makes things a lot more complicated. If he was any other boy, then it would have been easier. Just a flirt or two and that's it, but given the fact that it's her brother it's harder for her, so she searches way to be around him and maybe does stupid things, because love makes you do strange things. She could have easily said "fuck off with your stupid bet, I ain't cleaning anything shit", but no she cleans his room, because in her heart she wants to do nice things to him, but can she admit that to him? Of course not! He's her older brother. This isn't Alabama.
The fact that she's asking for money doesn't make her a gold digger. If you already have a job and have a younger brother/sister, you tend to do a lot of things for them, more expensive gifts, they tend to ask for money. It's normal. I'll give you one simple example your little brother wants to go out with a girl, but he's ashamed to ask your mother for money because she'll start asking him questions so he comes to you. Does that make him a gold digger? No! That makes him a little brother. The same thing goes for Tris, the fact that she's asking for money it's normal in a family. Does she really need those money? Who knows. Maybe she wants to do something nice for her brother but doesn't have the money. A nice lingerie is expensive this days. If she tells her mother that she needs sexy lingerie she'll be a bit curious for the reason, because she knows that she doesn't have a boyfriend so what would she do with that. It's tricky.
Like I said before so many times, this game is not only about sex. If you want sex, in the header of the website there is a link called THEPORNDUDE. You have everything you want there. This game is telling a story and I intend to tell it. The sex is just here for the ride.