IMO, I don't like her. The pictures show a poor hind end and back legs, her headset shows she isn't relaxed under saddle, and the ad is on Craig's List, NOT a horse selling site AND that "needs an experienced rider," which we know is code for a hard-to-handle-horse. That tells me that the owner wants to sell her quickly and get rid of a problem horse.
For trail riding I prefer a calm, almost too slow and slightly lazy horse who doesn't care if I don't ride all of the time and won't spook when birds fly up, or something out of the ordinary approaches. I believe that this mare would be trouble on the trail.
When I was horse-shopping I considered a barrel racer. This gelding was ~9yo, and on the road showing 40/52 weeks a year. I don't have the energy to work with one that fit, and I KNOW that we would be battling each other. I think this mare will fight you.
YOUR OP asked for opinions, remember?