The setting was very different from Georgia Nicolson's world- Tallulah is doing a performance art program in Yorkshire, where there is pretty much nothing. Well, there's a pub, of course, as this IS England, but that's about it.
Tallulah was also obsessed with boys, a little less obsessed with makeup, didn't break as many rules, and just couldn't figure out why she started doing Irish dancing whenever her mind went blank. She was very obsessed with her knees and lack of corkers and came across as misunderstood. And she adored her older cousin Georgia, who gave her a fake mustache which she did in the end find a use for.
Withering Tights was more of a 'I stumbled into a performing arts school and oh look I found out my unique talent' type of story, whereas with Georgia, well, she pretty much lived in a fantasy land.