Does iTunes Match delete songs already on an iOS device?

This was raised in another thread but not definitively answered. Suppose I've got an iPod with 500 songs on it. I turn iTunes Match on, giving that iPod wifi access to my library of 19,000 songs.

My wife uses this iPod; she's out doing a workout without wifi access. Will her 500 songs still be there? Or is there a brand new huge library from which we have to start over and download songs?

Thanks, that helps. I am assuming that when you are not connected to wifi, it just shows the artists/albums/songs that have been downloaded to the device. When you are connected to wifi, how are the downloaded songs shown? Is there a separate playlist or category for them?

Last night I tried it on my wife's iPod Touch. It seems to be working, and it does not appear to have deleted any existing music on the iPod.