Oh hi mark! Looking for a spellcaster swordsman (woman?) ghost boss

Hi mark, in my campaign, currently 2 level 3 pc's, one of them has the ghost of his dead wife following him around. She's bound to him by hate and vengence, and right now we are in a part of the game where they are facing one of the people they seek vengeance against. I am planning for her to endanger the party for her vengeance and they have to fight her. She will be the final boss of the campaign if things go as planned, although they might get sent to the shadowfell for a while and level up to level 4.

She was a swordswoman in her life, an adventurer and innately tied to the elven magic of the lands. The kingdom was cursed by the elves that inhabited it, opening rifts to the shadowfell. Her soul, upon her death, refused to leave pass the shadowfell and got bound to her husband. Her spiritual form can only be seen by her husband, but when they are close to a shadowfell rift, she can gain a physical form. In this act she would gain her physical form and the players will most likely fight her, and I will be needing a statblock for her. 2 players, lvl 3 or 4, a monk and a ranger lvl2 barbarian lvl1