Sometimes people who are toxic to you are only showing you their bad side to manipulate you or get something out of you because they need something emotionally that they can't get. (That should be somewhat flattering tbh but that's a discussion for another day.) Sometimes those same people will show literally everyone else their good side.

And sometimes it's the exact opposite. Sometimes someone will be toxic or a jerk to everyone except for you. If that's the case you're probably the only person they actually love or like. They also have realized that you're not easily manipulated.