Demoted after one loss at 0 lp with a d/c player friend loses 2 and still silver 3 at 0 lp?

can i get an explanation on y i got demoted after 1 loss in silver 3 and my friend is silver 3 with 2 losses she was under me in lp at 0 lp got 2 losses she will be on her third loss before demotion and i got demoted right away ? this is not fair and funny how i was the only person not feeding in the two games lol, my friend is a sweet heart btw nothing against her, just feel like this game isnt really fair when people i play with silver 1's tell me im really good fair team plz?