can she place the 7 and 8 intellect cards?
Yes. I don't see why she couldn't. It's like placing any other usable/special card. Some cards are offensive, some defensive, and some both. ;)
Yes she can, since it would be a useable power card by her. But of course, it can only be used defensively.
and still vulnerable to duplication
Can she place 7&8 any power cards? I think yes cuz her GRID is 8...