1)
I know every router I have owned I have been able to add restrictions to what computers can access the internet and at what times. The only exceptions I have seen to this are some of the wireless routers which come from your internet provider which are severely restricted in what you can do.
With my old Linksys WRT-100 I believe it is off hand it's under "access restrictions" other routers I have had, had it under different settings.
2)
You might be able to go into the BIOs and disable the built in wireless card and ethernet port there, if not you can surely do that with in windows with the drivers. (Right click properties on "Computer" and "Device Manager" will bring you to where you want) And this will work as long as she is not too tech savy. In fact I do this next time you confiscate the computer.
3)
Other option is to buy a cheap $20 safe and confiscate her laptop battery if it's removeable and power cord. She can look at her laptop all she wants but it's useless. I know when I caught my little nephew playing his nintendo wii late one night when everyone was asleep I sent him off to bed, I knew he was going to do it again so I acted like I went to sleep and walked out again 5min latter and busted him again. I sent him off to bed again, left the nintendo wii there with it still turned on and everything but took the AVI cables so it won't display picture or sound to the TV, and took the cable to the cable box so he can look at the TV/Wii with the lights and everything but nothing is displayed (yes I am evil, and gave him false hope).
4)
I can tell you if you install chrome remote desktop you can also see if the computer is online and remotely access the computer if it is. It will tell you if the computer is online, not that it is actively being used, she could just be downloading something well she is sleeping. Though if you were going to go this route I just use it to bust her to make her thing twice before being on late at night to make her suspicious that you know everything that is going on, and just not tell her you put it on her computer.
Or you can be evil and do what I would do and use a different remote access program that won't give the person in front of the computer a button to click to log them and use that to remote access it when she is online and just take over the mouse/keyboard and start closing down windows, opening programs, etc. Stuff to make her think she has been hacked/virus/etc. But that only if your evil. (That is what I personally do, than have the router disable her computer internet access after certain times or somehow have the router setup to do something wierd and mess with her internet connection when she isn't suppose to be online. As having the internet taken away is bad, but having the false impression your getting away with it while your being messed with to the point where you give up on using the internet is annoying on another level. And I already feel sorry for my future children if they try to pull this on me, thanks to this thread.)
TIP:
Keep an eye on the other computers if she has access to them if you do this. Beyond that expect a bit fit when you do this. Though personally I go the wireless router route if you can, especially if the router is located in your room or someplace she won't have access to. If it is somewhere she has access to and no other computers than disable her ethernet port so she can't bypass the wireless and just plug right in.
EDITED IN:
Just googled parental controls turns out it's built into Windows 7. You can turn on times when she is allowed to log in, access to what programs, etc. I knew it sounded familar, chances are she can bypass it if she is a bit tech savy, never heard of anyone using this. I am a bit too old for that to be used on anyone I know. Worst I heard of was some parental control setup on 2 of my friends computers in high school, all they did was learn to use a few words in spanish to bypass it but that was about 10yr ago.
http://windows.microsoft.com/en-us/windows7/products/fe...