It's exceedingly common for littles to seem to "get it" with a day or a few weeks of successful experiences. And of course Mommy is thinking things like "success; no more diapers; what a clever kid I've got; it's all uphill from here; I'm so proud!" etc.
And it's exceedingly common for kids to lose interest or to seem suddenly baffled by the whole process. This is most frequent in younger kids, or those who have had some big, upsetting change in their life, but it can happen to just about any child.
It's baffling from Mommy's point of view, and so discouraging. Parents are extremely reluctant to let a child "regress" and will often fight that with every tactic they can think of.
I personally think this is more likely to harm the process than help it. If we trust the child's first experimental successes, why shouldn't we support their whole process? Your daughter may genuinely be baffled by something about the process, or she may simply realize in some deep, genuine place in her little soul that she's just not quite ready to accept that long-term commitment to getting to the potty every time without accidents. She may need some time to reconsider the advantages of potty over diapers.
If she is sensing your dismay or tension, this can easily drive a bigger wedge between her and the potty. She probably doesn't 'think' about this so much as feel it, but she may be genuinely anxious about pleasing or disappointing you, and that would quite reasonably take her focus away from her bodily sensations. This process, for her, must be about her, not about you.
If I were in your shoes, I would soft-pedal the whole thing for a few weeks or even months, if that's what it takes. Assure your daughter that she's growing every day, and as soon as she's ready, she'll be able to use the potty. Wait for further leading from her that she wants to try again. And she will.
Meanwhile, keep all potty messages and education positive and upbeat, but don't be wildly enthusiastic in pushing it, or she will not be able to get her emotional legs under her. Too much parental eagerness tends to thwart children, no matter what it is they are trying to master. It takes inward focus to succeed with a new skill (and this is true for grownups, too!).
Here's a wonderful, informative website you might find helpful. It gives a few variations on"readiness" checklists, plus tips on various training strategies, the best ages to start them, and the advantages and disadvantages of each approach: http://www.parentingscience.com/toilet-training-readiness...