Riten is right but somewhere in travel.state.gov I read that the person entering US should have a clear purpose NOT other than visiting US as tourist (or something like that). Get a reason ready at the port of entry that you are in US this time to attend ___'s marriage, _____or ______engagement, _______'s delivery. To see more places doesn't sound much logical in this case because she visited US twice before. She should be good.