hi! can I play hunted alone?

If you want to yes.

perfect now to pre-order PC version...

I wonder how well the AI handles itself when you play alone. Like in RE5 Shiva would freaking chase me around with healing supplies when I had a damn paper cut lol.

It's quite different from RE5.
First, for the most part, your buddy AI can hold their own; provide them with skills and spells and they will use them-not only for themselves but to set your kills (Caddoc will levitate heavy armored enemies, making it easier for E'lara to pot-shot them). As far as healing, if you go down but not out, your buddy AI will always throw a regen vial your way, even in the throws of combat. If your buddy AI doesn't have any regen vials but you do, you'll automatically drop yours, so the buddy can run over and pick it up and heal you.
Hope this helps.

The players actually tend to give you a fair amount of space. And if you go down during combat, they can throw a health vial from across the screen.