Limewire is not the place somebody would get information about people downloading files. It is the ISPs (Internet Service Provider) that could release information and data regarding people downloading and sharing files protected by copyright laws.
I have no idea about the respective laws in the UK, but for me it seems the girl was caught due to sharing thousands of files and the circumstance that there are people around that try to find those who share masses of files to make an example out of them and scare others away from file sharing.
You can read here to get a clearer picture:
http://www.eff.org/IP/P2P/RIAAatTWO_FINAL.pdf 