A former Columbia Falls High School foreign exchange student has been charged in Yellowstone County District Court with a felony charge of fabricating evidence relating to a sexual assault.

Christina Nadine Nelson, formerly Christina Mark, pleaded not guilty Dec. 20 and was released after posting a $20,000 bond.

According to court records, a staff person at the Billings Clinic called police on Aug. 10 at about 11 p.m. to report that a woman was being treated there for sexual assault.

Nelson told police that she was leaving her job at Planned Parenthood in Billings Heights at about 5:30 p.m. when a former boyfriend approached her in the parking area. She said she told him she was married now and to go away. She claimed he slapped her in the face, punched her in the stomach and took her to a vehicle where he raped her.

Nelson then joined friends at a downtown brewery for a drink and got home about 7 p.m. She then went to a gym with her husband to work out. After showering, they sat in a sauna and hot tub and had unprotected sex after returning home. She told her husband about the alleged rape at about 10 p.m., and he took her to the clinic.

A detective spoke to the former boyfriend, who met Nelson at Rocky Mountain College and dated her from November 2009 to about June 2011. The man said he was in Seattle from Aug. 9 through Aug. 18 and had receipts and photos to back up his account.

Surveillance video from Nelson’s workplace showed her and a co-worker getting into their vehicles and driving away and no sign of the former boyfriend or his vehicle. A detective reported having trouble re-contacting Nelson until she sent an e-mail on Aug. 29 saying she didn’t want to press charges.

Further investigation revealed that Nelson had made similar rape reports in the past, including two in 2009 and two in April this year.

In 2009, Nelson, then Christina Mark, a foreign exchange student from Germany, claimed she was raped by a fellow student at Columbia Falls High School on the night of the prom. Charges filed against the boy were dropped after Nelson declined to testify, but the boy was suspended from school for several months.