It seems that someone has decided to try & "fix" the Sweet Suspense page here by claiming that there had been a fourth member added, but that she had dropped out for reasons unknown, possibly because she didn't want to be a part of a group. From all the Google searches I have done, I have found nothing that confirms this at all. There are no articles online nor any photos that can confirm if there was a fourth member. Also there have been no reports of anyone who works for the show coming forward and saying that this is true.
As far as I or anyone else here knows, there is no girl named Katie who was a member of Sweet Suspense. Sweet Suspense is Summer, Celine, and Millie, and that's it. I would very highly recommend that whoever is putting this Katie girl's name on the page had better stop because from I have mentioned before, there was and has never been a fourth member of Sweet Suspense.