It’s all hit and miss, trial and error I’m afraid! Recommendations for saddles are always a bit of a gamble as what works for one person might be the most hateful instrument of nether-torture for another!
we’ve been through:
nasty OEM saddle – ok for short rides
WTB Rocket V – okish for MTB, tolerable on short Roadie rides
Specialized Mk1 riva 155mm – ok on MTB and medium rides on Roadie
Specialized Mk2 riva 155mm – ok on short MTB, no good on Roadie
Specialized Mk1 riva 143mm (re-measured bottom!) – ok on MTB so far, not tried on Roadie yet
Bontrager WSD somethingorother – er, no good, I won’t give you the description she gave me of what it did down there, but it didn’t sound pleasant!
Both Spesh and Bontrager seem to have a reasonable range of models for women, my suggestion would be get measured, then try sitting ona few in shop if possible to see how they feel, then pick one (in cheaper cro-mo rail guise) and ride for a while, see how you get on. If all good then buy lighter posher version, if not then try another model.
How is her positioning on the bike? you mentioned she’ll be using one of yours, make sure it actually fits her and you adjust as necessary* as position can have a massive impact on how and where you support your weight, something that might seem trivial like a slightly too long cockpit can cause you to tilt forward on the saddle to reach the bars and put too much weight on the wrong places.
Is she already using padded shorts? if not then get some!
* I sense you might not have done this if swapping saddles was going to be too much faff, did you look at things like bar width, stem length/reach, saddle fore/aft position etc? or does she luckily magically fit your bike?
My GF and I are pretty much the same height, she’s only an inch or so shorter, and we can both ride the same size frames but the rest of the fit is so different that we can’t swap bikes without problems.
