Didn't she speak to her mother that evening about the last minute preparations for the wedding?
I don't think that's dispositive. Far too often, weddings become an event for the bride's parents, and in particular the bride's mother. For all we know, her mother might be a control freak and the daughter was afraid to tell mommy dearest to call off a wedding for 600 of their closest friends and relatives because she is in love with someone else. Of course I'm just speculating, but I would rather think that she eloped with her true love than become the victim of foul play.