I saw somebody mention this a while back. The term "Favorite Person" is just inaccurate on so many levels it feels like. FPs can be somebody you hardly know, somebody you don't want to be attached to, and/or just Not your favorite person; as well as the fact that it's just a very indistinct term, which makes it difficult to use when you want to reference BPD specifically. Which is why I feel like "Fixated Person" makes a lot more sense. That person is your fixation, not always your favorite. I hope it'll get used more often, it just feels more appropriate and distinguished.