Sienna Miller is slamming reports that she is cheating on her boyfriend with divorcing Hollywood actor Sean Penn. Sean is divorcing his wife Robin Wright Penn after eleven years of marriage and was recently spotted cuddling up at a New York hotel with the British actress, the New York Daily News reports:

“Sienna was sitting on Sean’s lap,” according the source. “She was dressed very sexily. She had her arm around his neck.”

Sienna calls the rumors “outrageously untrue,” she insists she and Sean are just friends. Sienna’s spokesman says: “Sienna is a very good friend of Robin. She adores and respects Robin.”