I have a 20 year old full time college student works part time can i file her on my taxes

You can probably claim her as a qualifying child dependent. Here are the tests:

1. The child must be your son, daughter, stepchild, foster chld, brother, sister, half brother, half sister, stepbrother, stepsister, or a descendant of any of them.

2. The child must be (a) under age 19 at the end of the year, (b) under age 24 at the end of the year and a full-time student, or (c) any age and permanently and totally disabled.

3. The child must have lived with you for more than half of the year. Temporary absences while away at college are considered living with you.

4. The child must not have provided more than half of his or her own support for the year.

5. If the child meets the rules to be a qualifying child of more than one person, you must be the person entitled to claim the child as a qualifying child. 

6. The child must be a U.S. citizen or U.S., Canada or Mexico resident for some portion of the year.

7. The child must be younger than you (or your spouse, if filing jointly) unless disabled.

Depending on how much and what type of income she had, she may be required to file her own tax return. If she does and you can claim her, she must indicate on her return that she can be claimed by someone else.