Hi L.,
What's happening here is pretty simple to fix. When a preschooler goes potty successfully for several days in a row—you now know she can do it. As soon as she's been successful a preschooler moves to the next stage of potty training, the stage no one tells you about, the testing phase.
This is the developmental part of the process. Your daughter has an unconscious developmental need to see what happens when she doesn't do as she was asked. So she pee-pees and poo-poo’s on the floor, to see what happens.
To solve this tell her, "You can pee and poop in the potty or you can have a diaper, you decide!"
If she decides to go potty and then turns around and pees on the floor, immediately take her in and put a diaper on her. No need to talk about it actions speak 1,000 times louder than words.
You may be thinking, but she can get the diaper off in 2 seconds flat! Try duct tape on the diaper to secure it, most parents can’t get it off!
Make sure to be supportive as she cries and begs you to let her go potty. Don’t say, “well okay, since you promise.” Don't play the game here it will just turn into a power struggle. Allow her to wear the diaper for about 10 minutes and then ask her if she’s ready to try again in the potty this time?
If you do say anything try “ I know you don’t like this, we will try again in a few minutes to go potty, what shall we do together until we try again?”
Don't use punishment for potty training. Be as unimpressed as possible when she has an accident or does it on purpose. Be as excited as possible when she goes in the potty.
Laying down the boundary so she knows the only place you poop and pee is in the potty, plus your tone of voice and body language all send her the message you need to go in the potty only. Punishment says, you’re wrong and you’re bad and must be punished, and that isn’t the case with potty training, it simply a case of learning. Looking for more solutions like this, check out, www.proactiveparenting.net
Good luck, The Mommie Mentor