Brittany Stricker, 20, is said to have slept with the teen, 14, every other day during a six-month romance, reports The Journal Star.
Stricker and the teen initially denied the affair but are said to have later changed their stories, it has been claimed.
She was pregnant when their alleged affair began but gave birth to a son on July 2.
The newborn’s father is said to be an unnamed Marine, Stricker posted on Facebook.
“Beginning in March there were two reports…with concerns about the victim being involved in a sexual relationship with (the defendant). ”
Stricker was arrested on Tuesday and charged with first-degree sexual assault of a minor by US law chiefs on Thursday.
It comes after cops in Lincoln, Nebraska, received reports in March expressing concerns over Stricker’s involvement with the boy.
Court documents reportedly revealed how the teen, then 15, later contacted police in July claiming he had sex with Stricker up to 100 times between January and June this year.
The couple are said to have been drunk on many occasions they allegedly slept together.
He also told officers how his friends had witnessed them sleeping together in the basement of her home, say reports citing paperwork filed at the time of Stricker’s arrest.
A probable cause affadavit published by The Smoking Gun said: “Beginning in March there were two reports…with concerns about the victim being involved in a sexual relationship with (the defendant).
“Both the victim and (defendant) were interviewed at that time and both denied a sexual relationship.
“On July 14 the victim contacted Lincoln Police to report additional information.”
The document continued: “The victim states that (the defendant) was aware of his age and multiple other parties confronted (the defendant) about the victim’s age and the inappropriateness of their sexual relationship.
“The victim states that friends have witnessed he and (the defendant) engaged in sexual intercourse.”
Stricker reportedly told police how “At times the victim acted older than 14…which helped her justify her actions.”
She is being held in jail and has been banned from contacting the boy ahead of a scheduled court appearance in August.