I read somewhere that it was that they refused to pay Farrel for her scenes used in the montage and, for that, she denied them the rights to her likeness.
Not quite.
Her agent had not been informed that her contribution was being used in a previous Season Seven episode (was it voice only, or image as well? in an Ezri/Worf episode) and they'd had to proceed to arbitration to get that matter of royalties owed resolved. Because of the pending judgment, the producers were unable to even ask about using more footage in the final episode. However, Terry Farrell was invited to the wrap party and did attend. She didn't deny them the use of the footage, but they forgot to ask first for the previous blunder.
This story comes via Richard Arnold, so some will choose not to believe his interpretation of events.