Asked why she did not come forward and report what happened until March 2012, she said: "I knew if I said anything, it would be my word against his and no one would believe me. I had no way out."
She will return to the stand on Monday for cross-examination by the defense, which is expected to attack her credibility. The defense says she lied about when she found a cellphone with text messages between her and the general and they argue when she confessed to a friend about the affair, she said she was not assaulted.
Earlier Friday, she testified in detail about how the affair developed, and said that Sinclair once threatened to kill her and her family — and "do it in a way no one would ever know" — if she ever told anyone about their relationship.
She was given immunity in exchange for her testimony. Adultery is a crime under military law.
In opening statements, prosecutor Lt. Col. Robert Stelle painted Sinclair as a man who used his authority to intimidate and coerce a female officer nearly 20 years his junior into sex.
Defense lawyers portrayed Sinclair as the victim of a desperately infatuated woman who became angry when she discovered that another woman had sent the general an email that closed with "I love you."
The defense also contends Sinclair is the target of overzealous prosecutors under political pressure to make an example of him, despite weak evidence and an accuser with a history of telling lies.
Defense attorney Ellen C. Brotman began her opening statement by reading the jury — composed of five two-star generals — excerpts from the woman's diary, written during the affair.
Even after he was alleged to have threatened to kill her loved ones, she wrote of her desire for him, Brotman said, and the only fear she expressed was that he might still love his wife.