Yes, you can claim a 24-year-old. When the income, relationship, and residence tests are met for an "other dependent", the age of the person doesn't matter.
For dependents that are also full-time students and under age 24, the income part is disregarded (this is where I think some confusion comes in).
Since your daughter failed to mention that she can be claimed as a dependent when she filed in January, as the others have mentioned, you will need to mail in your return for processing to claim her this year.
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