well, 1st of all, they say that for time-outs you should have 1 min per year the child is of age. and the older that they are, the more you can add minutes to the years they are of age. i think by 7, you should be up to 10 min...but AT LEAST 7 according to what they say.
of course, like i read in other suggestions...if this is a re-occurring problem, time-outs just aren't working anymore. i personally would have it carried out as far as you can. if it's no tv for a week, then it should be no matter where you are. the problem with that is that when she's at a friend's house, you can't expect the friend's mother to not let her kid not watch tv, or play on the internet just because your kid is being punished. i would just keep it to where if she were going somewhere with you, the punishment continues. BUT if she wants to play with friends, just tell her that they just have to come over. this way you can monitor what she is and is not doing and not have to worry about carrying out the punishment at a friend's house. and by making her bring a friend over, you can't be accused of grounding her AND taking away something...being that grounding means that you can't go anywhere, and can't do anything, AND most certainly can't have any friends over. or at least that's what grounding was when i was a kid. and to be honest, it worked so well, i think i was only grounded 2 times (both by my stepfather...and both my mother cut short...but it still worked)
i hope that something helps. it's just hard for some people to punish their kids for doing certain things that just seem menial. plus, some people think they're being too hard when they're barely doing any punishing, while others think they're not being too hard, and they're going way overboard. who's to say what's the proper punishment and what's not...i guess it all has to do with how bad she mis-behaved. good luck.