Boyfriends best friend on snap??

So I saw a girl on my boyfriends best friend list while he was sending a snap to his friend.. I think he knew I saw and deleted this girl when I wasn’t looking. A few minutes after, I asked him about the girl on his best friends list and he showed me his list and she wasn’t up there

In short, he said that he had no clue why the girl has on his best friends list and that it must be something wrong with Snapchat.. just looking for opinions and advice on whether this can really happen or not