Blake Lively hates looking "frumpy".

The 'Gossip Girl' actress - who was joined by her boyfriend and co-star Penn Badgley at the Metropolitan Museum of Art Costume Institute Gala on Monday (04.05.09) - often opts for "ethereal" outfits on the red carpet to stop her looking motherly.

She said: "My style is always changing, but I always tend to look for something more ethereal and flowy and not as straight. I don't like anything too frumpy."

The 21-year-old beauty - who has been dating the 22-year-old actor since they met on the set of the US show - wore a blue Versace gown at the exclusive gala evening.

She said: "I just love deep blue. I think it's so stunning. Everything about this dress, I just love."

Penn has revealed his girlfriend often checks her wardrobe choices with him first.

He explained: "She asks me what I think and I do the same to her, but ultimately we can wear what we want."

However, the blonde beauty insists she has no body image worries and is very relaxed about her appearance.

When asked about her fitness regime, she said: "Ask me in a month. I've been on vacation, so nothing. I ate a chicken pot pie before I came here!"

(China Dailly/Agencies May 7, 2009)