The actress was spotted with the 28 year-old bank heir last Saturday at the Live Earth concert in New Jersey. The two also shared a romantic dinner together at the Stanton Social in New York on Monday.
A witness at the restaurant told Us Weekly magazine, "They flirted and touched throughout their meal. They were really into each other."
Tatler magazine named David de Rothschild the second hottest bachelor, after Prince William, but before Prince Harry and Hugh Grant.