Hi Cathy! The 1890s is WAY too late for an "Indian massacre" of a wagon train, especially anywhere between San Antonio and Dallas. This area (I live in the area) was pretty modern/civilized at that time and Texas had already "controlled" the Native American population: http://www.tshaonline.org/handbook/online/articles/II/bzi1.htmlhttp://www.tshaonline.org/handbook/online/articles/II/bzi1.html
My experience with family legends is that they are MOSTLY true...but sometimes the crucial details get garbled. Maybe it happened to a relative, but made a better story told in first person? I'll also mention that if it was a massacre...how did she survive?
My advice is to keep an open mind to alternative possibilites. And if you want further verifications, you might contact the Austin History Center (they answer single questions via email), the respective county historical societies (Bell, Williamson, Burnet, Travis, etc.) and/or the Texas State Historical Society.