It is perhaps unfair to 'blame' Theresa May for the lack of cooperation on the subject of 'Reciprocal Arrangements'.
I think there is either a selective memory loss, or possibly no knowledge of the EU statements on the subject by Donald Tusk and Angela Merkel for example?
www.telegraph.co.uk/news/2016/11/29/donald-tusk-accuses-british-voters-backed-brexit-creating-anxiety/
'Angela Merkel and Donald Tusk on Tuesday united to block Theresa May's attempt to fast-track a deal which would have created an amnesty for British ex-pats and EU migrants in the UK post-Brexit.
Mrs May had proposed that EU workers currently living in the UK be allowed to remain in exchange for an agreement which gives British expats in the European Union the same rights.
She had hoped to announce a deal within weeks but while more than 20 EU nations have signalled they are prepared to agree to a reciprocal arrangement, Mrs Merkel has rebuffed Mrs May's attempts to come to an agreement.
Her position was then backed by the president of the European Council, Mr Tusk, who on Tuesday said that Mrs May and British voters had created "anxiety and uncertainty" for migrants. He told Mrs May she must trigger Article 50 – the formal mechanism for leaving the European Union – immediately to dispel those fears.'.
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www.theguardian.com/politics/2016/nov/29/donald-tusk-turns-on-tories-in-row-over-rights-of-eu-citizens-in-uk
'Tusk said the EU “stands ready” to negotiate Britain’s exit from the EU, including reciprocal rights, but could only do so ' once the process formally begins '. “Let me reiterate, however, that the decision about triggering article 50 belongs only to the UK, which we fully respect,” he said.'
-u
www.independent.co.uk/news/uk/politics/brexit-theresa-may-angela-merkel-eu-migrants-deal-a7445261.html
'But Ms May's attempt at a “reciprocity deal”, which would have guaranteed the existing rights of around 1.2 million British people on the continent and millions of EU migrants in the UK, was blocked by the German Chancellor.'.
It is a folly to keep banging on about what should / could happen , it is simply not the case any party can 'dictate' the terms no matter how unsavoury the subject matter.
The best we can hope for is the political elite stop being so b----y pathetic , work for a common good and shut up about the need for a Federal Europe and Free Movement of People, both of which are quickly turning into nothing more than jokes.