heartseeker quinn

i've been wondering if the level 5 chest that gives a skin of a champion that you own will 100% give me the heartseeker quinn skin if i have all her other skins, considering it's a 975 skin, or u can get a skin that u already own? im asking since im tired of gambling my money away, and im willing to make a new account for this skin alone, since the other skins i like can be bought from the market