My object's WeChat name suddenly changed to "You are a bear". What does that mean?

Maybe you think too much. She may just want to change her name. She might find the name interesting. Otherwise, ask her directly, or it's not good to think for yourself. Why don't you ask her what she really thinks? If she does, you can change it. If she simply said that she just wanted to change it to this screen name, then she would think too much.