had pretty much the same thing happen with my mrs minus we had been togethor 4 yrs we got back togethor and she had been txtin someone the same under a birds name i found out she burst into tears we split up again then she went weird and wouldnt leave me alone realised what she had done and wanted us back togethor i gave it another chance and we have been 100% perfect for the last 2 months now

id say give it another chance ask her outright or at worst do a bit of undercover work and find out who it is mighjt be hard but worth it in the end it will tell ya either way if you are just parraniod!!!!