How to use canon lenses on nikon cameras?

My mom has a canon rebel xt, and she has about 3 lenses to go with it, all very expensive. I recently bought a nikon d3100, and i only have one lens, the 18-55mm. I have been looking for an adapter so I can use the canon lenses on the nikon camera, but all i can find are adapters for nikkor lenses to canon cameras! Do they not make them the other way around?

Canon EOS to Nikon Adapter Ring is custom-made by Cinevate to allow any Nikon lens to fit on a Canon EOS camera, including the popular 5D MkII and 7D, both of which are as well-regarded for their video as their stills. Constructed of long-lasting chrome-plated brass, the adapter ring gives your Canon SLR access to a full line of quality optics, from Nikon's own topnotch lenses to such third-party stalwarts as the Zeiss ZF primes. With this simple adapter, you'll more than double your camera's optical versatility, while maintaining each lens' focal length and full focusing ability, from macro to infinity.
http://www.bhphotovideo.com/...Nikon.html

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The Vello Canon EOS to Nikon AF Lens Adapter allows you to mount a Nikon AF lens to a Canon EOS camera. Besides for making financial sense, this allows you to use your favorite lens across different camera platforms. The lens adapter is designed to fit securely to the lens, yet can still be removed easily when not needed.

Note! Although the lens will fit physically, automatic diaphragm (AE metering) and other functions dependent on communication between the camera body and lens will be disrupted by the lens adapter. You will need to set exposures manually or meter in aperture priority (stop-down) mode. If the lens does not have a manual aperture collar, the aperture will be stopped down to its smallest f/stop. Focusing to infinity is retained.
http://www.bhphotovideo.com/...Nikon.html

Hope it is a help

There are Canon-to-Nikon adapters available, but don't bother. You'll lose in-camera metering, autofocus and you won't be able to focus to infinity.

Trade the 3100 for a Rebel or just buy Nikon lenses…

It's so difficult (and expensive) and you lose so much function, it just isn't worth the effort. Buy your own lenses.

There's no magic adapter. The ones you find are not worth the money.

A Nikon camera deserves a Nikon lens.

If Marker would have read what he copied and pasted he's have noticed that it is to put a Nikon lens on a Canon body. That can be done, with the loss of electronic communication as others have noted. It is because the Nikon F mount is narrower than the Canon EOS mount. For that very reason putting a Canon lens on a Nikon body could not be done. Well, it could be with an adapter that uses a corrector lens to allow infinity focus when the adapted lens is mounted too far forward. However, a decrease in image quality would be added to the ills of making that adaptation. If the lens lacks a mechanical aperture ring, then there's the added problem of the aperture stopping down to its highest f number with no electronic communication to tell it to open up more.