I found it--Here's an article from the dailymail that reported (AKA stole from past reports and interviews, haha) that says she sees Nichola whenever she's in London. Again, not definitive but I think that tips the scales toward her likely being in London.
Prince Harry's girlfriend Meghan Markle shares her anti-ageing secrets | Daily Mail Online
Also, it appears that Nichola is not scheduled to be in NYC until January 29th for work. So best guess is she probably isn't there yet.
Nicola also posted another photo on the same day that tags Good Vibes which is a yoga studio in London.....I guess we will see soon enough.