Egads! SOS about frame materials and nothing to do with the OP's question
lets try this
Here is the Trek:
Here is the Lemond:
Here is the roubaix
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Looking at the top two pictures does anyone want to take a guess why Elana may have been more comfortable on the Lemond than the Trek?? .....Time up! first thing I see is the Trek has a level top tube , The Lemond has about a 3 deg up slope and also a taller headtube. Our friend Elana possibly was more comfortable because the bars were a bit higher. also If we look up the specs, The Lemond comes with a slightly more shock absorbant 700 x 25c tires as opposed to the 700 x 23c tires on the Trek. I couldn't find much other diffrence from an ergonomic standpoint between the two
Next, looking at the Roubaix and comparing it to the Lemond Versailles, I can see why some people like the Roubaix, it has even more up slope in the top tube so we can raise the bars a bit more. The Roubaix's anatomic bars are flatter on top to make riding on the hoods less of a reach. On the down side The tires are 23c so it likely will have a slighty harsher ride than the Versailles. The harsher ride will likely be offset on the front end by the 72.5 degree headangle and 49mm rake on the Roubaix versus the 73.5 head angle and 45mm rake on the Versailles. The small diffrence in steering IMO might make the steering on the Versailles feel a bit lighter but the larger tire may cancel that out if it is noticeable at all.
In the 55-56cm sizes the Versailles and Roubaix have the same top tube length and only 1/2 deg difference in seat angle. The Fit between these two bikes will likely be similar and be worth comparing. None of the 3 bikes provide for fenders or rack mounts so frame material is not really germain to the arguemant. Any of the 3 materials are versatile enough to be used to create a ride that can be compliaint or harsh. You have to ride all of them to make an informed choice.
Now the 520.
The main negative thing that jumps out at me in comparison to the others is the level top tube. and of course there is no adjustment in the bars because Trek will not supply the Fork tube longer. This is not an insurmountable problem because you can get a extender to clamp on and raise the bars(yuk IMO). The top tube on the 520 is 1 cm shorter than the Roubaix and Versailles which can be cancelled out with a longer stem. seat angle is the same as the Roubaix .From the standpoint of ride If you were not going to load it with panniers it will probaly have a harsher ride though this is mostly canceled out by the larger 700x35c tires and longer wheelbase. The greater steering trail and longer wheelbase than the Versailles or Roubaix will probaly feel more stable and may require slightly more steering input when turning. Another thought one may want to consider is that if you are planning on riding in sagged groups and the group likes to ride hard and fast and you want to stay with them you will be at a slight disadvantage since the 520 will be a few pounds heavier than the other bikes. However one could put some lighter wheels and lighter tires on the 520 that would lighten up the bike a bit.
In closing I think for Elana's stated purpose and budget the Roubaix and Versailles are worthy choices but she also throw a leg over the 520. The 520 is a really nice ride just not a fast one IMO. Another bike similar to the versailles and Roubaix would be the
Bianchi Vigorelli it is a steel framed bike with mostly Ultegra componets. I rode one back in October it is IMO a good bike for a long day in the saddle .
Rick