Hello there,
(Wow.. looking back, I realize this is quite a long, drawn out and technical reply. I apologize if some of what I have said doesn't make sense or if it's too technical; I work for an ISP... hehe)
IMO, I would say the most likely "internet problem" is not actually a problem with the ISP, but a computer problem, and most likely the computer problem is related to spyware/adware. I would recommend burning a disk with Ad-Aware SE Personal and Spybot Search and Destroy on it (with updates to their definition files included on the disk) and scanning her computer for spyware/adware. In my experience, this will fix the majority of problems people have with their "internet".
However, before I would run spyware removal programs, I would check some basic settings on the computer, such as making sure the "Local Area Connection" or whatever they use to connect to the internet is enabled and receiving an IP address from whatever device they are plugged into (router, modem, etc.). If they are getting an IP address that IS NOT a 169.254.x.x address, then their internet connection is probably fine. However, if they have a router or some other device, and are getting an IP address, there could still be a problem with the router or the modem. In fact, the first thing I would personally do when I get there is power cycle (unplug the power for 10 seconds and plug it back in) their modem or router or whatever device(s) they have that have to do with the internet connection.
Now, if they are getting an IP address but the internet is still broken, try running those spyware scans, remove what they find, and restart the computer and see if that fixes it. It probably will.
If they aren't getting an IP address, or are getting a 169.254.x.x address, then either they don't have the cable plugged in, or their network card is broken, or something else is up with a device physically.
So, I would suggest trying the above stuff and see if that fixes it. It could be something really easy like what is above, or you could be in for a hair pulling experience. Have fun!