“And the Babylonians came to her into the bed of love. And they defiled her with their whoredom, and she was polluted with them, and her soul was alienated from them.”
The relationship had developed into an adulterous one. Jerusalem became wrapped up in Babylonian culture and religion and was thus further defiled. The point here is that Jerusalem had not been dragged screaming into dependence on Babylon but had openly embraced it. They had no one to blame but themselves. But the demands made also became excessive and resulted in alienation. It was a love-hate relationship. It was this alienation that would eventually destroy her.