i figured out! actually, I found the answer online.
snippets have a way to share with only one website or with all of the websites, I went inside the snippet I wanted to use in a sub website and clicked on the radio button that says “share with all”. After that, I had to use a prefix of the website short name I wanted to share from and enter the snippet name, here is the example:
{mydefault_site_snippetname}
“mydefault_site” <—is the website i’m sharing from
“snippetname” <—is the snippet name i’m wanting to use.
NOTE: you have to first go to your snippet and select to share with all websites on the bottom left hand of that snippet enty.
Enjoy!