After the siege of Home, on the Airship, speak to Cid a couple of times, and he will reveal the truth.

Anyways, she WAS taken to Bikanel along with the others of the party by Sin. However, when she reached Home and found Cid, the Guado found her (because at this point, Home was attacked by the Guado, and the siege still continued). So, they took her to Bevelle in order to wed Seymour (how this was done, I'm not sure).