Missed Period For A Week

Hi. My wife missed her period for a week (1st June is the 1st day of period). We thought she might be pregnant but until yesterday (8th June) she had spotting. We thought it was normal but today (9th June), she experienced heavy flow. Is it normal that her period came this late, as she never had period this late before or is it something to do with implantation bleeding. I'm confused. She did home pregnancy test on 7th June but turns out negative.