Period!!!!!!!!! help for sis?

my sis is 12 and has started (i havnt yet n im 13) she got her first period n told me it was very heavy the pad got full every 3-4 hours i think she lasted 8 days but got lighter. yesterday at school my friend had to let her borrow 1 of hers at 7 or 8pm she said theres abit of blood at night she used jus tissue as my mom had no more pads was goin 2 get sum in the mornin. she said it dot soaked about the same size as ur thumb(but put on a pad 4 school my mom jus gotem). now after school she says itz soaked up abut the size of her thumb but the plastic at the bottom has nothin in it. she wants to no if shell get heavy or will she stay like this