[rnnw62]

I don't have a yorkie girl I have a boy so I can't give you
a size estimate, but from your description I am 99% sure
she is indeed in heat. From my experience with other female
dogs in the past. At first onset of heat cycle sometimes
there is no swelling and little indications besides a little
blood such as what you are describing. Since you just had
the recent problem I would refer to your vet but be very
careful with her in the mean time.