>>718671530 (OP)
That line is playful and affectionate. Letβs break it down:
"You're gonna make β¦ swoon" To swoon means to faint or feel overwhelmed, often from excitement, admiration, or affection. In casual or playful speech, it usually means "youβre so cute/charming that it makes people melt."
"your big sisters" Refers to older sisters (whether literal or figurative). Sometimes "big sister" can also mean a protective or affectionate older-friend type.
"hearts swoon" Emphasizes that their hearts are melting with affection.
So, the whole phrase means something like:
"Youβre so cute/adorable/charming that your older sisters wonβt be able to handle it β theyβll just melt with affection for you."
Itβs said in a teasing, loving, almost doting way.