When to test?

My friend has irregular periods and today it has been 4 weeks since she had sex, I bought her a first response that tests 6 days early, and within a minute a faint line popped up, so i bought her another test from Walmart ( 88 cents ) and i told her to take with her first morning urine since she has diluted her pee from drinking so much water she couldn’t test again tonight .. thoughts?? I don’t have a good picture of the tests but 3 people saw the line including myself .. ( pink dye )