Reservist vs Active Duty Military

No, that is not considered Active Duty, however it is a temporary absence for the home if she intends to return to your home after training. If she meets the other requirements, you could claim her as your dependent. (If she intends to return to your home and does not supply more than half her own support). The housing and meals supplied by the Air Force does not count as her suppling her own support. 

If she was under 19 on Dec 31, 2024, and meets the requirements to be your dependent, claiming her could increase one of your credits such as the Earned Income Credit. 

Qualifying child

To qualify as a dependent, a child must also pass these tests:

• Relationship: Be your son, daughter, stepchild, eligible foster child, brother, sister, half-sister or -brother, stepbrother, stepsister, adopted child or the child of one of these
• Age: Be under age 19 or under 24 if a full-time student, or any age if permanently and totally disabled
• Residency: Live with you for more than half the year, with some exceptions
• Support: Get more than half their financial support from you
• Joint return: Not file as married filing jointly unless only to claim a refund of taxes paid or withheld

See the full rules for a qualifying child

Qualifying relative

A qualifying relative must meet general rules for dependents and pass these tests:

• Not a qualifying child: Isn't your qualifying child or the qualifying child of any other taxpayer
• Member of household or relationship: Lives with you all year as a member of your household or is a specific type of relative
• Gross income: Has gross income under $5,050
• Support: Gets more than half their financial support from you