Vicky has always been jealous of Charlotte. Vicky hates other women anyway, but I always felt she was especially resentful towards Charlotte. Char was the star of GS, and most people's favourite. Her weight loss DVD was more successful. Charlotte was prettier and slimmer, and naturally funny in her own way.
Vicky wanted to be the star but everyone hated her. So Vicky started acting like Charlotte, but she cannot pull it off. It was a total personality change.
The sly witch even spent the night in the shag pad with Gary, and I bet £50 stuff happened in Australia too. That must have really hurt Charlotte.