my dog is 13 months old and i think she has been mated with by the nextdoor neightbours dog what to do please help

Take her to your vets, for the "morning after" injection.    However, this will bring her into season again, within two-three weeks, so make sure that you keep her away from Next-door's dog during that period.   And arrange to have her spayed, in say, 8-10 weeks' time - i.e. around mid-way between seasons.   Otherwise you could go through the same thing again every time she comes into season.

Margot

Hi take her to your vet for the after mating injection, or if you dont wish to breed from her have her speyed at the same time.
good luck