Okay Ed,
When I had decided I wanted to do the switch and I wanted a Thinkpad, my search began. Even from just one manufacturer they have so many different models, not to mention a plethora of choices. I really thought it was hard.
However, since she already have an idea what she wants and at what size she wants it, may I suggest a T400 (14") with a screen resolution of 1440x900. You can also get a 12" X-series with that resolution (my X200s), but it might be a tad too much in dpi-department for an architect.
If you go to that site you can narrow down the search, if for nothing else, then to get a better overview over the models.
I ordered my two Thinkpads from Germany (with DK keyboard), and my GF's Thinky was bought here in Denmark. All of them were made to order, so to speak. Apparently that's how Thinkpads are sold (real Thinkpads, not the "Thinkpad SL" - bleh!).
The T400 has switchable graphics and you can get a caddy for an extra HDD instead of the optical drive, if so needed.
The W-series are utter workhorses, the T-series more of a compromise between portability and power, and the X-series are dedicated to portability.
Anyway, no matter what, check the resolution as many of their models comes in different resolutions and so. My X200s has the same resolution as my 15" MBP, but it's at the expense of a webcam. The X200s also comes with a much lower screen resolution , but then includes a webcam.
It's good to know exactly what model one wants and then go search for that model specifically (besides, say, "X200s", at the bottom of my computer the exact model number is - wait (had to look at the bottom) - 7469-5KG), that way you know exactly what the specs are on that specific computer.
Eh, I hope I havent confused you more than I have helped ...
Sod it!