This is They Say I Was Born a King's Daughter.
From Baka-Updates:
After spending most of her youth fielding the attention of countless wealthy suitors, Suhee Kim finally finds true love with a steady boyfriend named Jinsu Han. But then tragedy strikes, and Suhee is murdered in cold blood.
To Suhee's surprise, she is immediately reincarnated as a baby girl named Sanghee Kim, who just so happens to be a princess! Plus, she is fully conscious of her past life. There's just one problem: in this society, women are seen as totally inferior, even princesses. Appalled by the treatment of women, Sanghee is determined to change the kingdom's patriarchal ways. Will Sanghee be able to succeed, or will she be stuck living her second life being treated as a lowly woman?
The main character, Sanghee Kim, starts out as a young woman living in modern Korea, who is stabbed and killed by a man she recognises, but whose face is partially obscured from the reader by the hoodie he's wearing.
Sanghee then wakes up as a baby in another world. In this new world, she's actually a princess, but her father and two of her three brothers treat her with disdain, due to her sex. Only her eldest brother is kind to her.
When she gets older, she attends a magic academy, but isn't initially shown to manifest any powers.
Much later in the series, in chapter 120, she visits a pyramid with some of her classmates, and they're subsequently attacked by goblins. Sanghee then uses magic to heal her friends' injuries.

