On this episode of The Young and the Restless, Mac marries J.T. at the Chancellor mansion before they leave to D.C. Her wedding dress is similar to this one.
As for her jewelry, she is wearing a diamond circle pendant necklace like the one listed here.
$399.00 at Max & Chloe
Update 11/9: Mac is also wearing what appears to be a blue string bracelet with a silver hanging charm.
Her bracelet is similar to these options.
$47.00 at Swarovski
$3.00 at Avon