It could be that she's a little bit embarrassed/modest about having someone there watching her? I know Lindsay had a huge problem with people *knowing* he was in the toilet and for ages wouldn't do a poo in a public toilet or at preschool - he would do it at home. It took a long time for him to get over it and once he did he was fine. Do you think she is modest about it, especially if she isn't telling you she has a dirty nappy etc?