Lily Allen is amused by her decision to cover a Beyonce track tonight (19.09.13).

The 'Smile' hitmaker has been rehearing her unusual choice of song non-stop for her big performance at Martini's 150th birthday party in Lake Como, Italy, much to the distress of her beauty therapist.

Lily wrote on Twitter: ''I am doing a beyonce cover for tonight's @Martini_drinks 150th bday party tonight. #lolathon

''Sorry to the beauty therapist who just had to endure an hour of me singing along to a beyonce instrumental while she waxed my legs. (sic)''

Her curious fans tried to get the singer to divulge her choice of song to no avail, writing, ''which song sis?'', with yet another enthusing, ''Love You, Hate Beyonce! But her songs (i say hers but she's never wrote 1) cummin out of u may jus make them!!! (sic)''

Guests at the party will also be treated to performances by Lily's former 'Oh My God' collaborator Mark Ronson, as well as piano pro Chilly Gonzales.

Lily initially announced: ''gig tomorrow on lake como just @chillygonzales a piano and me. and @iamMarkRonson for afters @Martini_Tweets is 150years old n ting. (sic)''

The pop star has jetted off to Italy for the high-profile event, and killed time at the airport by celebrity spotting at London's Heathrow airport.

Lily posted yesterday (18.09.13): ''I am at heathrow airport , I have seen Kelly Osborne and her fiancé , Paloma faith, and Seal buying a laptop charger at dixons. #airports''