There are tons of other signs besides not talking that indicate your sister-in-law's aversion to you. For example, they might be tattletales by making negative comments about you to other family members. She might be controlling, judgmental, jealous, or even try to start fights over sore points that could fester between you and your spouse (via Parenting). Your sister-in-law might also try to manipulate you, project her feelings onto you, or even exaggerate things with words like 'always' or 'never' (via Hey Sigmund).

Even if your sister-in-law acts like this, there are ways to handle it without it becoming a long, drawn-out fight. Start by trying to understand where she is coming from ,such as a place of jealousy. Make your moves and talk to her while feeling empowered rather than feeling like you are being controlled. Take back the power you have within yourself and the relationship to address the issue, set boundaries, and resolve any conflict. 

This should be done with care and empathy, though. Own who you are, but choose your battles carefully, and know that you don't have to explain everything (via Hey Sigmund). She needs to do the same, but you might have to be the leader. Even if things get worse before they get better, it is worth fighting for more peaceful familial relationships, especially with your spouse's relatives.