Ashleigh Barty beat American 18th seed Alison Riske 6-3, 1-6, 6-4 and next plays two-time Wimbledon champion Petra Kvitova.
Alison Riske tied the knot with her long-time partner Stephen Amritraj, who is the son of former Indian Davis Cup player and captain Anand Amritraj.
Serena Williams came under enormous pressure from Alison Riske before prevailing in an engrossing contest, 6-4, 4-6, 6-3 in just over two hours.
Both players eliminated Chinese opponents in the semifinals on Saturday. USA's Alison Riske won the first nine games en route to a 6-0, 6-1 rout of Zheng Saisai, while Swiss Belinda Bencic advanced when hometown favorite Peng Shuai retired with a lower back injury while trailing 3-1.
Ana Ivanovic cruised to an easy 6-3, 6-0 win in the opening round of US Open.
Hantuchova, a 2008 Australian Open semi-finalist in her best Grand Slam run, has matched her best US Open showing from 2002 by reaching the final eight.