The only time I recall someone having to leave was last season when Jessi was hospitalized and could not perform for that show. In that case, they knew last minute and there was no time to teach someone else the choreography. I think they made the fair decision by letting Pasha perform with Melanie LaPatin. Jessi was not out of the competition at that point, she was just able to perform that night. They let her go the following night. (Too bad, she was my favorite.)

In this case, they apparently knew in advance enough that Jessica was not only not performing, but out of the competition. Obviously Comfort was at the rehearsals and they seemed to have equal rehearsal time. I do think that this was a fair decision by bringing the last girl kicked off back. All the guys needed partners. If America didn't like her, she will be gone tonight.