The 29-year-old, herself a former contestant on the reality show's regular edition, slammed her rivals after watching them enter the house on last night's launch show.
A feud between Thomas and Natasha emerged after they were both revealed as having had an affair with footballer Ryan Giggs, former brother-in-law to the latter.
"Just watching cbb catch up," she tweeted. "I love Natalie Cassidy and her task.' Wag' Nicola McLean is a fake. And as for the other one......."
Thomas later hit out at Twitter users who directed offensive language her way, writing: "Dear followers. If you wish to write me can u pls refrain from using 'disgusting words'. It takes too long to block u. Love."
The former Miss Wales claimed last May that she would be open to an appearance on Celebrity Big Brother.
Last month, Thomas was freed from accusations that she tried to blackmail Ryan Giggs while details of their affair were protected by a super injunction.