Well, when people consider buying a bike, most people will go with either a road or tri bike, but this bike looks like a hybrid with MTB bars and road tires. It sort of reminds me of my MTB when I put specialized fat boy slicks on them. If you had this bike already, I'd say use it to not spend any money, but to buy it, i'm not really sure.
It seems fine as a bike (steel is fine, more of a preference/parts are fine) but I don't really like this option for a triathlon. The reason is because she will be sitting up like on a MTB so she will be comfortable but not very aero at all. Adding aerobars to a MTB bar "may" work but it will look sort of frankensteinish. And I doubt it will be comfortable. Even when adding aero bars to a road bike, it's not as easy as just slapping them on. You still have to make some adjustments.
Why not just an entry level road bike? They have several brands out there for around the $600-$700 range. I personally like FELT as an entry level bike.
http://www.feltracing.com/06/home.html They have two models at $699 in the road bike section, the f24 and f90. They retail for $699 but you can probably find them cheaper, last years model or used.