Terry O'Neill, president of the National Organization for Women, said, "It's a very serious, bad message to send to other victims," adding that rape is already an underreported crime.
Prosecutors came to doubt the case, which once appeared strong, because of what they call "substantial credibility issues" related to Diallo's background and conduct.
Questions arose surrounding what happened immediately after the alleged attack and led the Manhattan District Attorney's office to consider whether to drop the charges amid concerns about Diallo's credibility.
Diallo said she was in the hall when Strauss-Kahn left the suite, but hotel records show she briefly went into another room, and then re-entered Strauss-Kahn's suite.
Diallo has also admitted to lying on her tax returns and lying about the details of a rape in her home country of Guinea that helped her to achieve asylum in the United States. But she says that it is irrelevant to what she says happened in Strauss-Kahn's hotel suite.
"I have made mistakes," Diallo conceded to ABC News in July. "But this man tried to rape me."
Strauss-Kahn has denied all charges. His attorneys have suggested the encounter in the Sofitel Hotel suite May 14 was consensual. His attorneys have portrayed Diallo as a woman out for money.
If charges against Strauss-Kahn are dismissed, a dramatic prosecution would end without answering the question of what really happened between one of the world's most powerful men and an immigrant maid inside the hotel suite.
Meanwhile, Diallo's civil lawsuit will continue, even though the criminal case against Strauss-Kahn is ending.
"He has already been served," Diallo's attorney, Douglas Wigdor, said. "He needs to defend."
Marcellus McRae, a trial lawyer in the Los Angeles office of Gibson Dunn, who is not involved in the case, said Diallo might lack the resources to engage in a contentious battle.
"And she still has myriad credibility problems," McRae said.