When the film begins, it is 1909, and Guinan, not yet 20 years old, is still living with her family; in reality, by that time, the 25-year-old Guinan had already been married and divorced once, the first of three marriages. In the film, sometime in the mid-1920's, a doctor diagnoses Guinan as having a heart condition, and gives her, at most, two years to live. In real life, she died of amoebic dysentery in 1933, age 49.
In the close-up of Texas on her white horse twirling a lariat, the rope is clearly an animation and not a real lariat.
Texas' hair and makeup are in the style of 1945, not the style of the period, more than twenty years earlier, in which the film is set.
When Mike Guinan is sitting on the bed in the bridal suite worrying about his potato crop, a shadow of the boom microphone moves on, then off the headboard.