I have a 6 year old sister. Whenever my mum isn't anywhere near her or sometimes out of her sight, she would start crying non-stop. This has been a problem for my mum as sometimes she needs to head out for work in the morning while my sister is sleeping. Not only that. Everyday after my mum drop her off in school and when she needs to leave for work, my sis starts crying. She would say things like, "I want mummy!" and "I like mummy!". Is there anything we can do to help as we are worried that all these might affect her development.