How can I address to my girlfriend that I do not want to hang-out with this specific friend?

My partner's friend occasionally invites both of us to hang-out but I am not comfortable with her friend. I had my own issues with that person and I honestly just dislike her. I have no issue with my partner hanging out with that friend, but I really do not like it when she makes me feel bad for always declining to come with her. She's implying that it's unfair since she would gladly accept my friend's invitation when given the chance. Should I just accept their invitation even if I'm totally against it?