The singer attended the rapper and his gal's nuptials at Babington House in Frome, Somerset, with her hubby Sam Cooper.
She wore a gorgeous vintage-looking monochrome maxi dress with a check board top and a keyhole cutout at the bust.
She paired her dress with towering black platforms, a black Chanel handbag, and a pair of Ray Bans.
Lily was, however, spotted not-so-stylishly sneaking off for a cheeky ciggie before the ceremony. Slapped wrists, Lil.
Wonder if she dipped into the collection for Millie's wedding? See pics of the nuptials here, and check out more Lily fashion moments below: