Transitioning from hybrid to road/cyclocross

[Lady Hamilton]

Unfortunately, anything with Ultegra would have to be used. Although, at the bike show I saw gorgeous Wilier road bike with Ultegra in my size 50% off for $2000.

[Crankin]

All of the bikes you mention are awesome, but I think you are right, in that you can probably get a road bike with 25 cm tires and be fine on packed dirt. I have the Silque (albeit, a carbon one) and I have no problem on smoother packed dirt. I am about half an inch taller than you and a couple of pounds heavier, and the Silque is the best fitting bike I've owned. I am on a 47 cm Silque, and I switched out the Trek bars for the Specialized short and shallow ones I've used for years. Specialized's sizing is different and I am pretty sure I would need a 44 cm Ruby. My friend, who is about 5' 2" has the 48 cm Ruby and it seems big to me.
I gave up trying to find a gravel or cyclocross bike. There's a few new ones for women that are in smaller sizes, but the geometry still comes out wrong for me. And, for a 3d bike, I am not going to spend 4K.

[Lady Hamilton]

Yes, there is not a whole lot out there. For instance, the new Checkpoint by Trek starts at size 49 frame, and has a standover of whopping 74 cm. Very few women under 5'3 would clear that. The clearance and the reach of that bike match size 53 WSD Domane!
Specialized Diverge comes in size 44 and has very tiny specs. I did not have a chance to try it, but size 48 was ok for me to ride and did not feel overly large. I would still get 44, if I were to buy it.

I think I am steering towards either buying the Dolce Evo I tried yesterday (if they give me the price it was offered at the bike show), or go with endurance road that has disks. There are a few last year's Synapses available with disks and Tiagra (and they are slightly less than Dolce Evo).

Or, otherwise, I will just wait for this year's Ruby to go on sale later this year. The future shock suspension is amazing, the bike is very beautiful, and fits very-very well. Specialized really went ahead of Trek this year, offering disks on all their bikes. MSRP on Ruby with 105 set is $430 less than comparable Domane. But, Domane has hydrolic breaks.

As far as comfort on packed dirt, I won't even have to go with 25 tires. Ruby Sport is 28, same is Cannondale Synapse. Trek Domane Disk is 32!

As far as fit goes, I found Trek Silque S5 47 and Ruby 48 fit very similarly. I wouldn't go down to 44 Ruby. I tried 48 yesterday and with saddle perfectly aligned with the bar both ruby and Dolce 48 are perfect for me. But, my Vita is also S, not XS. My legs and arms are a tad bit longer than average for 5'1.

[Crankin]

Ha, now I want to look at the Diverge.

[Lady Hamilton]

You should. It's a nice bike. What I have noticed almost immediately (I was out in the parking lot) is how much better it takes tight turns than my Vita Elite. I find Vita a very snappy bike, very nimble for a hybrid.
And also, the temptation of Diverge is that it's E5 aluminum, as opposed to A1.
Diverge 44 will fit you for sure. even 48 is a fairly small bike.