Alslam alikum I’ve been wondering for a while ,Allah forbid his mercy and rewards from a Muslim girl who doesn’t wear hijab?
Alaikumassalam wa rahmatullah,
It’s like any other sin. It’s not an ideal situation to be in since we get the most mercy from God when we are most obedient. But it doesn’t mean that you won’t have any rewards or mercy. Please see: Can you be a good Muslim woman without wearing the hijab?