She went into an interrogation that stretched over 11 hours. The authorities said she made conflicting statements implicating herself. Ms. Graswald told investigators that it “felt good knowing he was going to die.” She also said that his drowning had brought her “relief.” She was recorded in the interview room doing yoga poses and hopscotching.

In the interview on Friday she defended her behavior. She said she was hungry, thirsty and tired. “I was just being cooperative,” Ms. Graswald said. “I also felt like I couldn’t leave, that I couldn’t walk away at any time.”

Prosecutors said that she knew she was the beneficiary of life insurance policies belonging to Mr. Viafore worth about $250,000. She had also said that Mr. Viafore had pressured her to do sexual acts that she did not want to do, which the authorities also contended could have been a motivation to kill him.

But she disputed that.

“I was just at the wrong place at the wrong time, bottom line,” Ms. Graswald said, noting the rough conditions the couple ran into on the water. “I was in danger, too, just as much as he was. I just happened to survive, and now I’m guilty?”

Ms. Graswald, who was charged with second-degree murder, was about to stand trial this summer when prosecutors approached her lawyer with an offer of a reduced charge. With the trial looming, both sides acknowledged growing uncertainty.

Prosecutors noted that there was “little direct precedent, if any,” of a conviction for removing a plug from a kayak. Tests had found that removing the plug from the kayak was not enough in itself to cause the kayak to capsize, prosecutors said, and Mr. Viafore was not wearing a life jacket or a wet suit and the couple had alcohol with them on the trip. And in a case that would have largely turned on Ms. Graswald’s vacillating statements, prosecutors also said that her admissions did not add up to a direct confession.

(Prosecutors declined to address the case last week. “The case is over and as such we have no further comment,” said Christopher P. Borek, the chief assistant district attorney.)