jilt /dʒɪlt/ BrE AmE verb [transitive]
[ Date: 1600-1700 ; Origin: jilt 'woman who ends a relationship' (17-20 centuries) , probably from jillet 'girl who attracts sexual attention' (16-19 centuries) , from the female name Jill ]
to suddenly end a close romantic relationship with someone:
She jilted her fiancé just before the wedding.