
At shows dogs firstly are 6 months + and secondly already trained not to pull :)
It sounds like you're using a slip collar - though not sure, it could be a half check. Either way if she's not used to the lead yet (and ideally it would have been better to start training at home and in the garden) then it is probbly wiser to use a flat or rolled leather collar collar with a buckle. I'm sure you don't want her to develop negative associations on her first proper outings with the big wide world ;)
HTH, regards Teri