Thanks again folks. She went with the Giant Rapid 3, which supposedly has exactly the same frame as the Defy road bike (but no carbon fork). It has dual-pivot calipers and the 700 rims will take 25 or 23 tires. Similarly, it has Sora derailleurs (I think), which should work fine with Sora STI brake/shifter units.

I think that if she does decide she wants to set up the bike to be more road-focused she'll be in good shape.