I'm also a Lisbon fan and was just about to send you a link to my blog but I see Sandralist has done it for me! I like London in the winter too and also Prague. One advantage of Lisbon is that it's a lot cheaper than many of the places mentioned if that's a consideration for your daughter.
I'm a big fan of Rome in the winter (though you've been before), fewer people and it's a good combination with Naples.
"No-one with a brain chooses where to live or stay on the basis of weather."
That has to be one of the silliest statements I've seen recently. Of course people take the weather into consideration. Why do you think there are all those expats in the south of France, Spain, and Portugal? Why do you think people from the northern states of the US retire to Florida? Never heard of the snowbirds? Etc., etc.
The fact that you can't find anything interesting in Lisbon says more about you than it does about Lisbon.
Travelocity - Has anyone used them?