My vote is still for a Palm TX, after taking every factor into consideration.
http://www.palminfocenter.com/...lm-tx-handheld-review/
Good quality large screen (320x480, portrait or landscape configurable), decent formfactor (the build quality is a bit cheap but servicable), TONS of add-on software, especially in the medical field, wi-fi and 128mb RAM + SD slot. The wi-fi implementation on the TX is the best yet on a Palm OS-based device (which isn't saying much but still) and the Bluetooth is only 1.1 but it's functional for Hotsyncing.
Also, the TX is on Palm's list of Vista-supported devices by the latest Vista-compliant version of Palm Desktop so she's set if that's a concern.
Given that the TX is nearly 3 years old, it lacks a user-replacable battery and SDHC support. However, it does have a FAT32 driver onboard so you can use an "unofficial" 4gig SD card with no problems. But with HIPAA concerns coming into play, I think there is some sort of requirement that all data be stored locally in non-removable media? So, ther 128mb of RAM would really come in handy on the TX, as it has most of the essential apps built into ROM and Palm OS PRC & PDB files generally have much, much smaller footprints than WinMob-based devices. After a reset, you still have ~110mb free on a TX for user storage purposes.
If she can live without wi-fi and with just a Bluetooth & a 320x320 LCD, then the Tungsten E2 is a similar formfactor device, just with a tad older version of the OS/apps. It actually has a better quality LCD than the TX (18-bit color vs. 16-bit) and its battery lasts a very long time. Either the E2 or the TX support onscreen handwriting via Graffiti 2 or you can tap on an onscreen QWERTY keyboard.
You can get new TX's online for ~$250-ish or gently used examples on the various forums & E-Bay for ~$150ish. By now all of the bugs have been worked out and any Palm OS software still actively supported has long since been made TX-friendly.
From a PDA & smartphone standpoint (as of this very moment--haven't played with WinMob 6.1 much yet) I still prefer the speed, ease & elegance of Palm OS. And the thousands of cheap/free apps available online are really impossible to beat.
It also has a 3.5mm stereo headphone jack in case she wants to play a few tunes here & there. For what it's worth, the TX makes a surprisingly good poor man's PMP, with the screen in landscape mode & the headphone slot. I recommend CorePlayer or Kinoma (for commercial apps) or the discontinued but still available TCPMP (freeware) as excellent Palm OS media apps.
As far as Windows-based PDAs, the ONLY one I'd even consider is the massive (in size, power & cost) HP iPaq 210. It's a beast in every sense of the word but probably tremendous overkill for the job at hand:
http://www.mobiletechreview.com/HP-iPAQ-210.htm
P.S. While it's all the same when you really get down to it, Windows CE is pretty much resigned to "embedded" systems & instllations nowadays. For your average PDA, depending on the age of the device, you'll find either Pocket PC or Windows Mobile on it. Either way, the days of the dedicated PDA seem to be pretty much numbered, as the manufacturers are trying to push everyone to a converged device (higher-margin, less-cutting edge hardware & those juicy carrier agreements & contracts!)
Other alternatives could potentially be an iPod Touch or a Nokia N-series Internet table or even a smartphone (with or without service on it) but I'd personally stick to one of the 2 machines above. For PIM purposes, Palm OS still blows everything else away. For multimedia & data crunching, go WinMob. There's also a QVGA Hp IPaq 110 that's smaller & cheaper but less capable than the 210 mentioned above that might be a good fit as well. The 210 & 110 are, IIRC, the only PDAs on the market (at least in the US) to shop with Windows Mobile 6 standard.