She's Witch, Untriggered Werewolf, with Vampire Blood.
There is no such thing as human-witch hybrid or werewolf-human hybrid. Even if you are only a werewolf through one parent (Like Tyler Lockwood), you are still considered a full blooded werewolf. Same with witches.
And despite the fact that she was born and concieved under unusual circumstances, she still should not be able to keep her magic if she dies and comes back as a vampire. Because just like with every other witch, there is absolutely nothing stopping nature from stopping her from having access to magic as a vampire.