I've dealt with this, unfortunately.
My step-sister seems to have a vendetta against Jackson, or maybe it's me, who knows. She will kiss and love on my dads two dogs and the minute Jackson would come over, she'd be all "ew, get away from me!" It hurt my feelings... because Jackson is like my child, and he doesn't get excited to see very many people (he's shy, so he has a select few that he's SUPER excited to see!) One day, I had had enough.... we were out by the pool and he jumped up on her lap and she pushed him off of her, and I started screaming at her, LOL. She started screaming back, we got in a huge fight... well now, the two get along just fine for the most part. She's come to accept how 'passionate' I'm gonna be about my dog, and that Jackson loves her to pieces, so now they are friends, though we rarely see my step-sister anyways.