I think i found an ok way to use her.
1) Respec her
2) put everything into spellpower and constitution ONLY(don't increase willpower at all)
3) Make sure to put a skill pt into Blood of the First
4) equip her with the Talisman of Saarebaas
5) get her friendship (it's not that hard)
4 and 5 will boost her blood magic so at this point you get a pretty good ratio of 4 mana to 1 health. That means an ability that costs 20 mana now costs 5 health. You can also get the staff has boosts blood magic to get a 5:1 ratio but in my opinion not necessary. Get a more powerful staff like Stone's Breath instead.
6) get sustained abilities that suits your playing style such as rock armor (20% of mana to sustain) , elemental weapon (10%) , arcane shield, death syphon (important to blood mage for obvious reasons) etc...make sure they add up to 50% exactly.
It doesn't matter that your willpower is super low as these abilities take up a percentage not an actual amount
What i do with her before battle:
A) Activate all 3 buff spells that take 50% of mana to upkeep in total

Activate Blood of the First.
C) Activate a 5th buff spell or save it for your first attack spell (she will use up her remaining mana before using health)
Hope this helps.