Trying to upgrade her to a new model is basically impossible. At the time we bought it if you went to any carrier store the Windows phones were clearly second class citizens with the best models not present. Carriers like T-Mobile wouldn't even sell you a decent model because they don't carry them at all and if you buy one separately you find that carrier specific stuff (tethering) is broken.
With Windows phone it was really like they weren't even trying to move units. Sure they built the software and hardware, but actual retail presence seemed pretty broken.
They also failed at continuity. There is no Lumia 1020 successor. The lineup in general seems fragmented with no regular predictable upgrade path and iteration.