Toddler

my step daughter has been potty trained for 1.5 years. she just turned 4 and started preschool this year. she holds her pee in all day until she gets home but she also does it at home and at my sisters house and we are there often so she is familiar with her house. she waits until she absolutely cannot hold it anymore. what can i do to help her? i always ask her when we get to our destination if she has to go potty but she always says no. 5 minutes later we barely miss having an accident. thinking i might have to bring it up with her teacher to work with her at school. any advice??