This will cost the UK heavily I expect... The EU will want their pound of flesh.I've thought this for a while.
I think there is 1 more chance to get her deal through. She needs to get the ERG on board and she'll hope that the risk of a lengthy delay will be enough to do this. They join and I'm pretty certain there are around 25/30 Labour brexiteers that will follow suit so she may not even need the DUP vote. Alternatively, if the EU decline an extension, she will work on the other side of the house who will want to avoid a no deal Brexit.
Failing the above, the only real option open is to agree a long tem extension to article 50 and fight a general lection in the hope that somebody gets a majority.
I think you're right though. The ERG will baulk at the thought of no Brexit.