1. Quartz vs. mechanical movement. The first is easy maintenance, the latter requires periodic maintenance but is preferred by most on this forum for a variety of reasons.
2. If mechanical movement: Manual vs. automatic (self) winding. Auto requires little thought whereas manual requires a daily wind (usually daily). Either works well and is more a personal preference.
3. Size: many women now are moving to larger watches from the older, petite watches deemed women's watches in the past. The fashion fad is toward larger watches for both genders.
4. Bracelet vs. strap: Straps allow for a change of colors, skins, etc. Many women (and men) enjoy changing the look of the watch with strap changes.
5. Ruggedness: That is, ability to wear daily no matter the activity vs. using as a "dress" piece. For daily wear, swimming, bathing, etc. Rolex makes fine timepieces. As you move toward mechanical watches which are more decorated (jeweled externally) and with more complications the water resistance as well as "bump" resistance usually begins to diminish.
Suggestions:
Patek is generally "understated elegance". The Calatravas certainly so. There is a line for women--Twenty--four which is attractive (in quartz as well as mechanical, I believe). And many other styles work well on women.
The GP Cat's Eye is a beautiful piece for women. My wife is enamored of this particular line and finds them quite attractive (and she generally likes the more restrained pieces).
Rolex, as mentioned, is an attractive watch which one can wear in almost any setting or activity level. Most makers also have an example of a "sports" watch which can be worn in most settings/activities. They tend toward the larger size. A bracelet is more practical for wearing the watch in water.
Hope this helps.
tempusfugit