Ay, mahirap sabihin talaga based sa description lang, mamsh, implantation bleeding is usually very light at spotting lang, kaya kung malakas na ngayon ang period niya, mas parang delayed period na siya o irregular cycle lang for this month, which happens. Best way to know for sure is mag-take ng pregnancy test or visit the doctor para ma-confirm, lalo na kung concerned kayo, they can give her a proper check-up at explain kung bakit nag-shift ang cycle niya this time.