Hi J.,
It sounds like a little a little positive behavioral modification might help. Have you ever read any of the Berenstain Bear books to your daughter? My kids absolutely loved them. They address common fears and issues faced by kids and offer easy and sensible solutions. There's one called "The Berenstain Bears and the Bad Habit" (or something like that) and we used the method in that book for all sorts of behavior modification. Basically, the method works this way:
Give your child 10 pennies (or nickles, dimes, even dollars is that makes sense to you) that she can keep in her pocket so they act as a constant reminder of what she is supposed to do. Have her pick out a small prize that she really wants that will "cost" 10 cents. Tell her that every time she doesn't wipe, she will have to give you one of the pennies. (You can use the evidence on her panties to monitor her wiping.) At the end of 10 days, she will have somewhere between 0 and 10 pennies left. If she has all 10 pennies, she can "buy" the prize. If not, she will have to wait until she has been able to save 10 pennies. Start the process again.
You can repeat this as many times as you need to until the bad habit is broken and a new habit has been set. As she starts to get better about wiping, you can start increasing the number of days she has to behave correctly and offer prizes that cost more so that she will have to save for longer.
Not only have I found that the process works well for breaking a bad habit, but it's also great for teaching young kids that delaying gratification can mean bigger rewards. You can offer her the small prize at 10 cents, but also offer a bigger prize at 15 or 20 cents, and tell her that she can get the small prize now, or continue saving her pennies until she has enough for the bigger prize.
BTW, another good book in the series is about going to Kindergarten. I think it's title is "The Berenstain Bears go to School." You can find these books at www.berenstainbears.com.
Good Luck!