You cannot claim her if she claims herself by filing jointly with her husband.
Because she was in college for at least five months of the year, she meets the full-time studen exemption, so she CAN file Married Filing Separately and give up her exemption to you.
How much did she make in her job? If the amount was less than $15,000, she is probably in the 10% tax bracket. It would probably be more advantageous for you to claim her, but you need her cooperation, because the decision whether to claim her own exemption or let you claim is irrevocably hers alone.
Suggest you get together with the married couple and discuss this in detail. Do the returns both ways and offer to reimburse them for the tax savings they lose by letting you claim her. If, as I suspect, you are in the 25% tax bracket, you will still come out ahead even if you have to write them a check. That way, it's a win-win situation.
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