... I don't think Kyoko intentionally based Natsu on her mom, maybe but there was help in Natsu's development and it was the name tag confetti incident, though Natsu was at least semi developed and I don't know where that came from... Natsu lases out to relieve her stress and I'm not sure that's what Kyoko's mom does, I don't think she 'likes' to relieve her stress.
I don't think Kyoko was inspired on her mother to create Natsu. Natsu was a perfect student that got everything in her hand, looks, brain etc. Natsu bully her friend out of boredom not bcause hatred or anything.
I agree Natsu is very different to Kyoko's mom, but I think Kyoko based Natsu's poker face and her "elegance" on Saena...
I wonder what would be Saena's reaction if she knew Kyoko was inspired on her to make the character Natsu ...