I am looking to buy an ASUS netbook running a version of Linux. Can my daughter install and use windows live messenger via Linux?

As far as I know, Windows Live Messenger won't work in Linux. It does not work with wine at least.

Those netbooks, however, ship right away with pidgin. With Pidgin, she will be able to connect to the Live Network and chat with all her friends without a problem. If she uses webcam, however, it won't work.

In that case, you may consider aMSN, an open source IM which tries to simulate the look, feel and features of MSN Messenger. It has also Webcam support. It is, without a doubt, the closest you will get of Live Messenger. Try that with your machine first and see how it feels. If you think it is good enough, then go ahead and get the netbook.

If you/she does not like either Pidgin or aMSN, you may consider, in that case, getting a netbook with Windows pre-installed instead...