The mother of a missing Ohio teenager issued a desperate plea Sunday for the missing honor student's safe return after authorities charged her boyfriend with obstruction of justice in her disappearance. 

Seventeen-year-old Abigail "Abbi" Obermiller of Huron County, Ohio, was last seen around midnight on June 7 inside her grandmother's home, approximately 10 miles from her parents' residence in Norwalk. 

In an interview with FoxNews.com, Abbi's mother, Rose Obermiller, described her daughter as a straight-A student with no history of behavioral problems. She also described the girl's boyfriend, 21-year-old Robert "Bobby" Young, as "very possessive" and "controlling." 

Investigators believe the girl left her grandmother's home willingly, citing a note found inside one of her notebooks that indicated problems with her family. 

Rose Obermiller said that both she and her husband, James, disapproved of Young, who they say became increasingly possessive over their daughter since the couple began dating last August. 

"She was upset because we didn't like her boyfriend," Overmiller said. "And I think they just made up their mind to get together and leave."

Obermiller said Young often dictated what her daughter wore and controlled where she went and with whom she associated. 

"He didn't even want her near her friends during prom," Obermiller said. "She had this beautiful prom dress and she had to sit on the sidelines." 

Police allege that Young sent Abbi a string of text messages prior to her disappearance that implicated his involvement in the case. 

"It's clear he [boyfriend] sent her text messages of when to leave the house and was aware of who was picking her up," Norwalk Police Sgt. Jim Fulton told Fox 8. 

Young has pleaded not guilty in the case and is reportedly scheduled to appear in court on July 7.

"I don't know where she is. I have no idea where to start," he reportedly told the station, adding that he voluntarily allowed police to search the home that he shares with his sister.

An honor student and class treasurer at South Central High School in Greenwich, Ohio, Abbi is described as 5 feet10 inches tall with brown hair and blue eyes, weighing approximately 120 lbs. Obermiller said her daughter, a senior aspiring to become a researcher in oncology, had no behavioral issues and was a model student. 

"This is very out of character for Abbi," she said. 

Police have labeled the girl's disappearance "endangered," and are urging anyone with information about the case to contact the Norwalk Police Department at 419-663-6780.

Click here to read more on this story from Fox8.com 

FoxNews.com's Cristina Corbin contributed to this report