They probably aren’t doing as great as it looks - runners typically (almost always) think about their twin constantly while acting like they’ve moved on completely. They’re running from themselves, not from you, but that doesn’t make it hurt less when you’re the one left dealing with all the feelings they’re avoiding.
That said, you’ve got to be honest with yourself if you want to figure out if this is your twin flame or not.
Your mirror soul will bring up shadows but you both actually heal and grow from them. Karmics bring up shadows and you just stay stuck in low vibration patterns. Twin flames feel safe even when they’re painful - like you can be fully yourself. Karmics make you walk on eggshells. Twin flames are reciprocal, both people feel it. Karmics are often an one-sided obsession.
If after months or years they’re still doing the same shit, not growing, not coming back, not even acknowledging the connection? That’s usually karmic. The universe isn’t this cruel - it won’t trap you with someone who makes you miserable forever just for “spiritual growth.” Sometimes the lesson is learning to walk away from what’s destroying you.
You’re allowed to feel however you feel right now. Hatred included.