Doggy life

It is official, my she-dog is masochist and optimist in one (2 for the price of 1). Today I went with her to vet, to sterilize her. And she was happy when she saw the she-vet. (She-vet gave her 4or more shots by the last visit), but she waggled her tail like mad.
When she got her sleep shot, still was happy to see the she-vet.
I dont know now - she-vet can prod, poke her, but she clearly loves her. Or has she really such masochistic nature? Or she-vet got such charming aura, that all dogs love her till death? Im curious.