My sister-in-law always spends her own money talking about it.

Can't you afford to hide if you can't afford it? Since you are often calculated by her, stay away from her so that she can't find a chance to calculate you. If you can't avoid meeting her, let yourself be more careful, be alert everywhere, and be wary of each other. When you meet your sister-in-law, you should learn to refuse, and don't be afraid to hurt your feelings. Your sister-in-law really doesn't treat you as one of her own. What are you worried about? Of course, if you think your brother can make a decision, then you can also talk to your brother about it.