As a reminder, Evolution Media produces only RHOC and RHOBH. All the other Housewife series are produced by other production companies, which may handle things differently -- so I can't speak for them.
Viewer Guess12 loved last year and wanted to know why we felt the need to add anyone? Actually, there were several reasons. Camille was in the middle of a custody battle that was taking up a lot of her time, so she couldn’t commit to shooting full time. Also, Lisa was covering the royal wedding for HLN, which you saw in tonight's episode, so she wasn't as available as we would’ve liked. With some of the ladies busy with other activities it felt natural to introduce a few new faces.
Caliviewer wants to know what the difference is between being a full Housewife and a "friend of a housewife?" Good question! The full Housewives are the central personalities we are following throughout the show, so the biggest difference is that the "friends of housewives" we feature alongside our Housewives are not followed individually. Meaning, you'll never see a scene of Brandi with her friends, or of Dana and her fiancée, without any of the Housewives present. They also are not in the main titles, and don't have graphic title cards.