I've never had my nose broken, but I'm guessing it's very painful and likely traumatic if I was completely on my own. I can imagine my hand going automatically to my nose in her position if I associated the presence of other people with being hurt. It would be a physical memory being triggered; her hand could go up in a reenaction of the earlier event.

As the paragraph is in Bond's POV, I would take any conclusions he came up with to be dubious. In this section, at least, her actions aren't completely unbelievable, if one ignores Bond's reflections as skewed and not actually a good assessment of reality.