There's a whole bunch of ICQ clients for linux... you could look for them at www.freshmeat.net ... just do a search for ICQ client... when I'm in linux, I use micq... it's a text-based ICQ client
As for converting the contact list from Win ICQ client to the Linux one, uhm.... I don't know if it's possible or not. Well, you could always write down her ICQ number somewhere, and later add her back in...