You're right, but there are practical reasons for her getting a Mac. I could fix any problems she has with it, but if she has problems with windows I'm much less well versed. I also just want her to have a well made computer that works and isn't so buggy and prone to break.
The only reasons I think anyone ever would need a Windows computer as opposed to a Mac is if they are a gamer, or if they use professional applications that are not available on a Mac. But people that use a computer to surf the web mostly, which is what she primarily does on her computer, I don't see why they wouldn't want to use a Mac. I guess I'm biased though since I've been using Macs since I was 12 years old.
BTW: love your quote, "In the end, you might either have to get a fangirl or can only shag your Mac."
i think you are over estimating how easy it is to break a pc. unless your girlfriend is into downloading like hardcore porn or something like that, you're probably not going to have to many problems.
and microsoft security essentials is the only antivirus i use and it keeps my win 7 working just fine.
and getting a mac just because you do nothing but surf the web is probably the worst reason to get a mac. mac and pc surf the internet about the same. macs arent as magical as steve would have you believe.