Her school lets out at 2:25. She lives about six miles from school, which doesn't mean much - it could take anywhere from 15 minutes to an hour for her to get home. (My kids lived two miles from school but were last off their bus - took 45 minutes to get home!)
So she got off the bus, either went in the house and came back out, or just played in the yard straight off the bus.
A "family member" saw her playing in the yard at 3:45 - at that point she could have been out there only a few minutes, or up to an hour, depending on when the bus dropped her off.
If she lives with her mother, then that family member would probably be her mother...yes? Or an older sibling? Or....? Kind of odd that they aren't mentioning who saw her last.
Then they looked out around 5 pm for her, and didn't see her.