I would still wait until the second heat cycle. (Some people even prefer to wait until the 3rd) IMO, the 1st heat cycle, not an age, is an indication that the dog's reproductive system is maturing. (Kind of like with humans...some get there earlier than others.
) Allowing her ample time to mature is crucial and gives ample time for any would-be health issues that can be brought on by the variance in hormones to present themselves.