Usually you'll want to take Eul's if you've had a rough/horrible early game. No point in getting bloodstone if you'll keep dying. Also take Eul's if you're getting focused in team fights. Self-cast to avoid dmg while your ult deals it.
Usually AC is better for the -5 armor (so your spirits do more dmg), you'll want to take shiva if you're having trouble keeping up with your food, it also gives more mana.
No point in ever getting Bloodstone on her honestly. That much mana regen is overkill on an hero that doesn't really use that much mana.