Masked (Marauders Era Fanfiction)

(PLEASE READ ALL OF DESCRIPTION)
(IS NOW PICKED UP BY @FayeEMNaib)
The only thing about Sirius Black that Mrs. Black was proud of was his arranged marriage to Mirabella Wylherst. Both were 2 years of age when the deal was made, and both the Noble House of Black and the Wylhersts, strong followers of the Dark Lord, were happy about it (the Blacks seemed not to mind that Mirabella was 3/4s veela).

The two grew up together and were utterly smitten. Sadly they parted at age 6, the Wylherst family relocating to France and they had no communication ever since.

6 years later a Mirabella arrived at Hogwarts, the first transfer in centuries. Entering third year was the despised half-blood Mirabella Vwelroy who quickly became the top of the Marauders' victim list, terrorised each and every day. To Hogwarts she was the ugly, clumsy, dumb, bumbling, shy Slytherin that everyone would bully at every chance.

Well Sirius Black's fiancee was outstanding at magic and acting after all, sent to Hogwarts to see how her young lover was getting along.

So what exactly happens when Mirabella's heart has finally had enough after 2 years and decides to get revenge on the whole school and her worst bully Sirius Black, HER Sirius?

And why does Mirabella's heartbreak seem to be connected to the surprise attack launched on Hogwarts by a furious Lord Voldemort?