If your daughter meets the tests to be claimed by you, she cannot claim herself. If she did claim herself, she must prepare, print and mail an amended tax return form 1040X to indicate that she can be claimed by someone else. If she made less than $4000, the change will have not affect on her taxes because she would not have a tax liability in either case.
You can claim her on your tax return but you will have to print and mail it to get it accepted. It takes up to 16 weeks for an amended return to be processed so you can't wait that long to try to efile your return again and get it accepted.
