Thanks for your reply.
Right, she is using Windows 7 x64, and running Eset Nod AV. She's in NZ, same as me - same room in fact!!

We're both running wireless 801.11n, and I can connect and play without any kind of problem. She's using an older gfx card, nVidia 8800 GT I believe; which runs ME1 and 2 without any problems on Steam (the difference appears to be Origin...).
There are no multiple users on her PC - just her. Hopefully this helps!!