But for a winter scarf what would be better?
It all depends. Some people prefer crochet or knitting, for some it depends on the pattern. For me, crochet came first, I just wasn't coordinated enough to manage 2 needles and I didn't even know about Continental knitting which is the only way I can knit. I think the English method requires more coordination, at least for me.
As for which is better for you, if you really are starting at the beginning for knitting and crochet, give both a try and then see what you want to do. It could be a simple decision based on which you find easier to do. Learn both, IMHO, as each has its good points for different projects.
There are lots of videos on this site that I find extremely helpful. I find the crochet videos this gal does are the best for me. http://www.youtube.com/watch?annotat...&v=79zZJjXRfSM
You have a very lucky girlfriend.