Was she in on it? The girl? Was she Daisy? In Robertson's book, Locke finds all of these meetings and dates with someone named Daisy, but everytime he shows up, no one is there...except The Girl. Thoughts?
It is interesting that Locke sees the girl in London before their paths cross again in Spain. That would lead me to believe that she is not there by accident. Remember that Locke says, "I think Daisy is a man," when the girl is thumbing through the calendar, remarking how Daisy must be a favorite of Robertson's. That may simply be another way of showing how at sea Locke is. So no definite answers, sorry, just some more speculation. I saw this film last week in New York and went back the next day to see it again, it was that compelling and visually stunning. Can't wait for the DVD.
On the commentary track with writer Mark Peploe it is mentioned the reason the girl is in London at that particular building because she is an architecture student and that was a modern building at the time and she was studying it. The same reason she is later at the Gaudi building in Barcelona. He mentions this as an example of the theme of coincidence in the movie.
I don't believe as some of the posters here that she was Robertson's wife (look at the age difference alone) or was playing Locke or "in on it" with the weapons dealers or the police or anyone. I think she was just a student that got swept up in an adventure with Locke and was just as clueless about everything that was going on as Locke was.
As far as the Mrs. Robertson / passport issue at Hotel de la Gloria in Osuna at the end of the movie that other posters have mentioned, I think the girl was just posing as Mrs. Robertson (as Wikipedia says), and not actually Mrs. Robertson. She could have used her ID/passport to check in but used a number of excuses as to why her last name is different such as that they had just eloped or she hasn't had her ID/passport updated since getting married, or that she decided to keep her last name in the marriage. Ultimately though, I’m not sure the passport mention was at all supposed to matter.
I think the entire point of having the clerk say "Mrs. Robertson" in the script was simply for a little added suspense of not being sure who Locke was going to find in the adjacent room before he reunites with the girl.
Btw, did the actress playing Rachel remind anyone else of Glenne Headly?
I thought it was completely clear: "Daisy" and all the other feminine names in Robertson's appointment book were code-names for his arms-smuggling business contacts. I wouldn't be surprised if Daisy was the code-name for Achebe (Ambroise Bia), the guy who bought the weapons. But it could have been any other customer too.