a 6-man noise marine squad w/blastmaster is a decent squad to sit back and hold your deployment zone... they have high 'I' + rapid firing weapons for close-in threats and in the meantime they can sit back and smack tanks.
as the others have said, give the codex a good read-through and then sit down and think about what you want to include!
though to get your girlfriend started with a few models, you could always pick her up the 'combat squad' box of chaos marines. it's cheap and gives her 5 basic marines she can use to start coming up with potential colour schemes!
cheers!
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"Who are you to question my methods?! A 'Puritan' is simply a coward who hides behind a veil of pretended faith and denounces his loyal brother as a traitor out of simple jealousy!"
- Inquisitor Odion |