If my dependent daughter studied abroad in 2016 from February through June, do I say that she lived in the US for the entire year, or for 7 months?

You will indicate that your daughter lived with you for the full year (12 months).  The IRS views temporary absences while the dependent child is away at school as time lived at home, (see below):

A parent may claim their child if they meet either the qualifying child or qualifying relative test as outlined below:

Qualifying Child

These 5 tests (all of them), will qualify a child as a dependent:

• Relationship: They must be your child, adopted child, foster-child, brother or sister, or a descendant of one of these (grand or nephew).
• Residence: They had to live with you in the same residence for more than half the year. Being away at school is considered as living at home. 
• Age: Must be under age 19 or under 24 and a full-time student for at least 5 months of the year. They can be any age if they are totally and permanently disabled.
• Support: child did not provide more than half of their own support during the year.
• Joint Support: The child cannot file a joint return for the year.