They are trying to E-file the taxes which will result in a rejection because of the situation. If they mail the return by the time they receive her return your amended return should be processed and there shouldn't be an issue. It takes up to 4 weeks for the IRS to start processing an amended return.
There is also a possibility she will need to show proof that she can claim the child as a dependent. This is generally what happens when 2 people claim the same child.
