My 4yo is in bed by 730p & usu awake/up 4 day by 7a. I don't know her exact sleep hours but she is miserable & tired 4+ days a week. Why could this be?

4yr old. Children are continually growing and changing thier habits. They also have mental stresses adults may not realise. If you realize a real problem with your childs health, for gods sake, take her to your pediatrician and get her examined.
Not restful sleep? A child may not be getting restful sleep, due to snoring, being in the "wrong" sleep stages, or other problems. Such a child can be tired in the daytime, and sometimes irritable or even hyperactive. Also, there may be a non-sleep issue, such as anemia, lead poisoning, medication side effects, thyroid imbalances, etc... A visit to the doctor, and maybe a sleep study & lab tests, can be helpful.