In English we add an 's' to a pronoun to show possession, like Elise's cat, but in Spanish the only way to show possessiveness is "el _ de ella" or a possessive article, which go
my: mi(s)
your: tu(s)
her/his: su(s)
our: nuestro(s)
y'alls (in spain): vuestro(s)
theirs, y'alls (in mexico): su(s)