Do you use LimeWire pro, or standard... since I seem to remember having read somewhere that one of the differences between the two, is the aptitude of the pro version to handle more peers together (then, obviously, more sources)
But, you mentionned also yourself that one of the differences with your girlfriend, appart of working on Windows (but I'm working on mac, and it's fine) is ALSO the ISP... I would give to that more then just one consideration! go and have a look on Lord of the ring's post just a bit higher... and follow the link... some ISPs can indeed produce funny things (or not so funny!).
I dunno if there are se same type of tests for LImeWire than for eD2k, but with the donkey, one can connect to some sites (one of them is bigwillystyle42), and they tell you if they succeded to communicate with your donkey... of course you could download the donkey just for the experiment...
An other site makes also all the tests to see what your protections are... so, you can see what ports or fully open or shut or stielthed, and removing for few secs all your protections, if some appears stil shut, you can know, then that it is from your ISP (by the way, some are almost always shut by them to prevent you to be a server) <https://www.grc.com/x/ne.dll?bh0bkyd2>.
Cheers