Theoretically it could happen. I've seen juries do stranger things. It will depend on how precise and detailed she can be about the alleged encounters and how believeable she comes across. It would help if he had an alibi or if he could demonstrate bias on her part. But if there is no physical evidence, to me that's good enough for reasonable doubt or at least you can make a good case for it. But he needs to get a good, experienced criminal defense attorney fast. Best of everything.