Let us assume Mrs Merkel is telling us the truth. She probably did say on her Greek phone call that the Greek General Election was in effect a referendum on the Euro, not that she wanted them to have a referendum on the Euro as well as a General Election.
It is still quite a change from her position last year, when she with France helped push a Greek Prime Minister out of office for daring to propose a referendum on European matters. These advocates of greater European integration have usually been against referenda, or have demanded re-runs when they get the “wrong” result.
The change of stance is presumably to try to force the Greek people to vote for a pro Euro pro EU loan package government. Mrs Merkel thinks the Greek people will do the right thing and vote the way she wishes if they understand that to do otherwise would mean their early exit from the Euro.
She might find meddling in other people’s elections from afar has unforeseen consequences. Greece may be wrong to think they can vote for the Euro and against ther loan package to sustain it. If they persist in this anti Merkel stance, there will have to be a face down between a new Greek government and an old German government over this very point. It is by no means clear who will win. Germany has in the past always backed down over more money and laxer rules.