If the baby is waking up earlier in the morning is she falling asleep at your house so you need to put her down? or is mom telling you that baby needs to go down because they woke up at a certain time?

Maybe you could try speaking to mom about the value of routine in schedule and see if she is on board to try and be more consistent with the sleep schedule?

Good luck It can be tough with a baby who is used to being able to sleep on their schedule.