Our son has had encopresis off and on for a few years now (although off for a long time at this point). We finally found what worked. It wasn't the laxatives, suppositories or mineral oil. Forget the charts. It was giving him bribes and having him go at the same time each day. At the beginning, we offered him a huge bribe to go -- say, maybe $20 -- to get him to not focus on the pain of such a big poop and to overcome his fear. He was motivated for that incentive! Then, we offered smaller but still meaningful rewards to him as he went each day. For our son, the best time proved to be right before bath time, because we were in routine mode then. It took a while, but he started to associate going with bath time and his body became used to things, too. Now, it doesn't hurt anymore to go since he's not holding for days, so it isn't a crying battle anymore. He often goes on his own now, which is a major achievement!
My big tip is to skip the diapers and focus on routine, routine, routine. Come up with a significant bribe to motivate her the first try (whatever would motivate your daughter ... think "wow" factor that she can't pass up) and then offer smaller rewards until the fear subsides and it's routine. If she's going every day, there won't be the tracks all over her panties anymore.
Encopresis is no fun and unfortunately will be a part of your life for a while. Don't beat yourself up over how you've handled it so far. We used to get angry at our son for having accidents, too, but understanding that it's a medical condition and not deliberate helps.
Good luck!