D1600 or 2488?
For ease of use, 16 mono tracks @ 16-bit (sufficient for putting down ideas), 16 individual faders, 16 pan knobs, touch screen... If she is not the technical type, the D1600 is the one.
If you want 12 mono tracks, 12 stereo paired tracks (24 tracks total) @ 24-bit (a slightly better sound quality), this is the one.
It is a tough call. However, assigning an input to a track is easier on the 2488, you press and hold the track input button, then press the track button. Done.
If you just want to put ideas down either will work.
In my opinion, the D1600 is designed to record, mix and master demo projects. The 2488 can do the same but gets a little more complicated on the mix end of things.
Hope this helps.