I am definately leaning toward the ECHO GT200i. It seems to have everything she likes. Light weight (under 10# empty), curved shaft, easy to start. It has a line head that makes it easy to load more string.
I like the large fuel capacity of the Echo as I usually have to fuel the lovely Mrs_Bob's current trimmer before she starts, and often again before she is finished.
I also like the easy start system of both the Echo and the Stihl (I still have not seen the Stihl in person but hope to today?).
I like the 2 year warrenty on both the Echo & the Stihl.
I prefer the Echo's head design, Stihl offers a similar head unit as an option. Both are priced under $200, which is nice.
The Stihl has a friendlier "sleek & contoured look" to their unit which may have some appeal to the wife, but functionally both appear to be basic units with simple controls.
The Stihl has a slightly bigger engine than the Echo, but both likely have MUCH more power than the inadequate unit she currently uses, so I think either way she would be happy.