The EU are (or would have been) open to other models than the one TM settled on.
They have suggested they would be open to alternatives when Corbyn approached them earlier this year. If a general election or new referendum had taken place, I think the EU would have granted an extension to hear what new alternative would emerge.
They are saying TM's deal is the only deal now, but that's because it was negotiated exhaustively in private already, and TM told them, essentially, she would take it to the MPs to get it rubber-stamped.
The MPs said no, it's their job, not hers, to hash out the big important compromises for the country, she should have consulted them before getting to that point and they don't like the deal she made, and they rejected it with the strongest defeat in parliamentary history.
The problem is leaving consensus building so late, so the EU spent all their negotiating efforts on TM's version of things, and they don't want to negotiate twice (unless a really good reason shows up that lines up with their principles).
