Living in London is very expensive. I own a flat in Pimlico (inherited when I 20.). I contemplated moving there lots when I was younger, but quickly realised that in order to live the lifestyle I like, I’d have to work ridiculously hard. Even though she owns property there, eating in the right restaurants, wearing good quality, fashionable clothing and even taxis would cost so much. If Steph would have stayed in London, she would have had to get a job to fund her lifestyle.
By choosing to play a damsel in distress in her ramshackle castle, her friends have to come to her, send her gifts and help her out. It cuts out so many of the living expenses. We know that prior to YT she spent almost nothing on renovating the chateau. All of her money has been spent on her lavish lifestyle - one she couldn’t have had while living in London.