How is is different from siddikatuha
Yes! Agreed! I think the real Fusha arabic people say : Saddiqatuha.
Here George refers to صديق as its بدل while ها is back to an unknown female person (ضمير غائب), who can be Judy, Carrie, or else. In short, the phrase above is correct.
If it is صديقة, it will be: صديقتُها رانيا, for example.
Sadiqatuha صديقتها could be if you talk in feminine as in صديقتها جودي sadiqatuha Judy (her friend(female) Judy) .. while as she says صديقها جورج sadiquha Jurj, it means her friend(male) George..