Fredzania Thompson and Earl Chatman were expecting a baby. The photographer was not hurt in the accident.
As she moved over to another track she was struck by a Union Pacific freight train.
'Burlington Northern had a train on their track coming and she turned back to the east to walk across the Union Pacific track and walked right in front of the Union Pacific train that was heading south'.
Despite being rushed to hospital she died soon afterward.
Fredzania can be seen smiling in a photo taken on the tracks taken just before the accident.
Authorities stopped traffic in Navasota for five hours following the accident as they conducted an investigation. The speed of the train on impact is unknown, but officials said a train traveling 50mph would need over a mile to come to a full stop, the Examiner reported.
Her fiancé, Darnell Chatman, 25, told Texas-based The Eagle newspaper that she called him around a fortnight ago to tell him the good news.
Fredzania Thompson poses for a photo moments before she is fatally struck by a train.
"That's definitely what she wanted to do", her mother Hakamie Stevenson told The Eagle.
"Zanie had the most attractive smile", fiancé Earl Chatman told the Eagle.
On Monday friends, family, and other mourners gathered at the site of the accident to pay their tributes to the teen on her birthday.
'Happy Birthday BabyGirl. We gonna miss you Zanie, just watch over us, I love you cousin', one person wrote.
A funeral service will be held 11 a.m. Saturday morning at the Brosig Auditorium in Navasota.
A GoFundMe page has been set up in Fredzania's name to help with the cost of funeral expenses.