Thanks for posting your query.
Since your girl friend's periods are already 7-8 days overdue when she did the test, we can rely on the test.
To be doubly sure, she can repeat the test with a highly sensitive pregnancy test strip 10 days post her due date of periods with a sensitive ( 20 - 25 mIU ) pregnancy test. This is best if done with a morning sample of urine.
In case the repeat test comes negative and the periods do not start till then, the causes of delayed periods need to be explored which include-
Hormonal imbalance, emotional upset, anxiety, stress, or other medical conditions that affect the ovaries, uterus, hypothalamus
, or pituitary gland
, post pill amennorhea , polycystic ovarian syndrome
or less frequently a pituitary tumor causing high prolactin levels or a hypothalamic disease
are other causes that may be the cause after the pregnancy is ruled out.
Hope this answers your query. I will be glad to answer the follow up queries that you have.
Please accept my answer in case you do not have further queries.
Wishing you good health.
Dr. Rakhi Tayal.