Practical Parenting Advice Online Parenting Course
Please report abuses to AndyGill@practicalparent.org.uk
They sometimes do that. It happened to my sister with her daughter. Just put her back in diapers or pull-ups and don't make a fuss.
She's maybe just far too involved in what she's doing to concern herself with going to the loo. Time and experience (hers not yours )will resolve it.