One of my dependents now works. How does this affect how I file? How does she file?

[Rainman12]

How old? How much earned? How paid (W-2 or cash)? Full-time student status? ...

[Jaynews]

16; less than $2000 ; w2; full time high school student

[LoganathanB]

Yes You can claim her as a qualifying child if she passes 

1. The age test, must be under the age of 19 or, if a full-time student, under the age of 24. There is no age limit if your child is permanently and totally disabled. 

2. Residency test, must live with you for more than 1/2 of the year. 

3. Support Test, You must be providing for more than 1/2 of their support even while they are working. 

4. Nobody else should claim her as a dependent

There is no limit for income.

She will become a qualifying relative if she fails the age test but passes all the other three tests. Then the income limit is $4300.

She can file her own return but should indicate that she is being claimed by you as dependent on your tax return.

Click on the link for more information

Dependent