That's not really comparable. It's her worst fear because deep down, she doesn't exactly hate it. Sure, it seems like a direct affront to her entire character on the surface, but the series has shown at multiple points that she does indeed care for Billy and Grim, while having a thing for Irwin. Even in the movie itself she nearly had a nervous breakdown after thinking Billy was gone for good.
It's her biggest fear because she sees that future as actually possible, if not inevitable. If it wasn't she wouldn't care nearly as much.