Phew! Big problems!
First off, you may find that wireless networks are insufficiently chunky to put through tv signals. Whichever is the newer standard; N I think, is the one you need if you persist with a wireless solution. I use powerline through an extender & that ain't brilliant, but just about keeps up.
I think possibly you're tv setup problem may be related to trying to scan via a network. Only a hunch on that, but it is normally done via the direct input from a satellite box or the tv card input. Can you connect an aerial to her pc directly?
As for the rest of it, you will probably find salvation on the green button -
The Green Button - Your Media Center Community
It started off as a media centre fan site & now MS own it. If you're stuck on media centre, the answer will be on there. Good luck!
Edit to say, oops, I see you're on N already. On tv, do you not just go straight to tv setup, i.e pop in the postcode, download the guide then go to scan? Scan always takes ages btw...