Can I use iTunes for more than one device?

I'm using iTunes for my iPhone. My wife is thinking about getting an iPhone and I'm wondering if she can use my itunes without syncing her phone to be exactly like mine since she doesn't like my music and I'm sure she will have different apps.

Yes, it will recognize them as separate devices.

Of course it can, and when you she sync her iPhone with the iTunes, she should uncheck your music, then the music can't be synced to her iPhone.