The queen is just a figurehead, with hardly any powers. May is, in reality, the head of the British government, therefore, head of state. Technicalities are worthless when practicalities matter more.
And, yeah, I know what you mean, but still, May is more important when it comes to the government in the UK.
Nope; head of state and head of government are still separate. All laws still require royal assent, the monarch still convenes and dissolves Parliament, and the monarch still has reserve powers (e.g. refusal of assent) although the leftists have bullied the monarchy into usually not using them. No foreign power recognizes the head of government as head of state, furthermore.