I think my sisters a furry and I don’t like it, what should I do?

This can be a really tough situation to navigate. The first thing to consider is why you don’t like this idea. 

Do you find it unusual or embarrassing? If so, it’s important to remember that many hobbies and fandoms look strange from the outside. Being a furry is usually just a creative interest or outlet, a way to express your interests.  

Are you worried about her safety? If she's interacting with people online, it's reasonable to care about things like privacy, age-appropriate communities, and online safety. Those concerns can be discussed without focusing on whether she's a furry. Possibly bring this up to your parents instead, as it may feel less condescending to her if it comes from the adults in her life. 

Is her behaviour affecting you directly? For example, if she's constantly bringing it up, using your belongings without permission for costumes, or making you uncomfortable in shared spaces, you can set boundaries about those specific behaviours.  

You don't have to share her interests or become a fan yourself. It's completely okay to dislike the hobby. The important question is whether she's doing anything harmful. If not, then the most practical approach is usually to let her enjoy her interests while maintaining your own boundaries.