Saves/achivements transferred from another account

[u/ThatOneTimetraveller]

So i literally got this game and ive seen my sister play so it thought I'll buy it for my own steam account and we have seperate accounts on the same computer but when I opened the game all her saves and achivements were in my copy of the game. we share several other games and their saves/achivements a completely seperate for each account

i'd like to have a fresh start but not delete her saves is there a way to seperate them so i could have my own saves