If she wasn't interested, she'd ignore his song and stay inside the lodge until he left.
It would then be up to the girl to decide a date for the wedding.
A Sioux man interested in courting might play love songs on his flute within hearing distance of the girl's family lodge.
If the girl was interested, she would come out of her tipi to listen, perhaps sneaking a sideways glance in his direction, but not making direct contact.
If a Sioux girl were interested in a particular young man, and was of marrying age, she might stand outside her family's tipi under close parental supervision, wrapped in a blanket and wait for him to come by.
When the man approached, she would open her blanket.