Nicole Kidman has splashed out on thousands of dollars worth of sexy underwear - to please alleged fiance Keith Urban.The 'Stepford Wives' actress bought the lingerie at the ultra-cool New York store Mixona to spice up her love life.An onlooker told Britain's Daily Mirror newspaper: "Nicole was in the store for hours and seemed really excited about revamping her underwear drawer."Since meeting Keith, Nicole's relaxed her diet and started working to give herself a curvier and sexier frame. There's a little more to her now."Nicole and Keith reportedly got engaged at Christmas and are due to tie the knot in March.Nicole - who was previously married to 'War Of The Worlds' actor Tom Cruise - is said to be thrilled to be engaged to the singer.A source close to the couple said: "Nicole is the happiest she's ever been in her life and doesn't want a long engagement.

"Keith proposed at Christmas and she was thrilled. They're happy and in love."