Where would you buy the Ruby from? If there's an LBS you know you'll be buying from, you might be able to get them to take some measurements (inseam, arm, shoulder) and then help you figure out which will probably fit you best. Ideally they'd have a good fitter to help you. Or talk to them about your options if you order one size and then find that it's not right.
Also +1 on pinson2's suggestion. I have a vague recollection that two of Specialized women's road bikes share the same geometry, though I'm not sure which ones.
- Gray 2010 carbon WSD road bike, Rivet Independence saddle
- Red hardtail 26" aluminum mountain bike, Bontrager Evoke WSD saddle
- Royal blue 2018 aluminum gravel bike, Rivet Pearl saddle
Gone but not forgotten:
- Silver 2003 aluminum road bike
- Two awesome worn out Juliana saddles