[T2 SPOILERS] Why did Kat say...?

Why did Kat say that they can never meet again? The abyss closes up and Kat is like: "We can never see each other again, the abyss says so. We need to promise to never meet again"

But like ... why? And also, they end up meeting again 27 years later - Which was/seemed planned so they ended up being forced to break the promise