I have a cat named charlotte and a female black lab whose name is sugar and is very friendly,?

my cat had kittens about 3 months ago and their starting to come outside, at first we wanted to tie my dog Sugar up so she saw them as "pets" and thats been working out fine she doesnt mind them running around at all, but yesterday one of the kittens ran past her and she just turned her head very quickly and nothing else. and i guess this made my cat very nervous and she lunged at her and we kept tryin to get her away from sugar and she kept running up to her trying to scratch her and making all kinds of wierd noises. and my question is basically is their a better way to have the kittens get used to my dog (and vice versa) without making my cat so nervous?