She then had a miniature whisky from her hotel at 2am to help her sleep, before arriving at Manchester Airport.
When she reported for duty seven hours later, she was still under the influence.
At the hearing yesterday, Rosehill admitted performing an aviation function while over the prescribed limit under the Railways and Transport Safety Act 2003.
Prosecuting, Nicola Yeadon, said: "To be fair to her in interview she gave a candid account and said she drunk more than usual the night before and felt fine for work but if she had known she was over the limit she would not have gone into work. She had her last drink at 2am.
"She apologised saying she was sorry and embarrassed at the arrest. She would not have flown if she knew she was over the limit. The legal limit is nine for this offence. She has no prior convictions and is a lady of previous good character."
Defending Rosehill, Paul Reddy explained how his client was embarrassed by her actions.
He said: "She had gone through security but had not flown. She's a US citizen and is from Chicago. She is absolutely humiliated by this matter.
"She has a 29-year career with the same airline and is a senior member of cabin crew who has been decorated in the past."
She was fined £140 ($249) and must also pay £85 ($151) legal costs and a £30 ($53) victim surcharge.
Rosehill is also currently suspended on full pay and faces a disciplinary hearing when she returns to the US.