Depends on what time of day it was used and when you both last had sex/when her last period was.
Eh she took it with first morning urine. And she is a week late
How old is she? There are a lot of factors that can cause a female to be late, and pregnancy is only one. If this is still based on the last post you made, I would imagine the test would be accurate and that she's not pregnant (being as pregnancy is slim enough in that situation anyways)
She is fifteen and was on bc due to irregular period but came off it the month before it happened