Can iTunes Match be shared over "i" devices?

I have an iPad and under my Apple ID, I set up an iTunes Match account.

My wife also has an iPad, as well as an iPhone. What I'd like to do is setup her iPad to access the iTunes Match account that I use, so that she can listen to the music herself.

I've read something about adding a device to iTunes Match however, it doesn't matter what I try, it still won't work. When I try the steps on my wife's iPad it tells me, rightly so, "You are not currently subscribed to iTunes Match". However, how do I add the 2nd iPad device to the iTunes Match account?

Duncan