It is OK as such. Although too much raw fish isnt not recommended. Excessive raw fish destroy a B-witamine, in unlucky cases they got seriously sick (the disease called yellow fat if I remember correctly - unpleasant disease).
Although some cats manage rich fish diet. As we all know, there are cat populations living more on less on fish...
So, tuna a couple of time a week is entirely OK. If you want to give it more often, be sure she gots extra vitamine E. - that is the remedy against this B-vitamine destroyer mentioned above.
Good luck!
ps. When you ask about kitten, you DO mean kitten? My answer is about adult cats, where I know this for hard facts even if I dont remember all details.
For kittens Im not equally sure. Although my guess is, it should be the same.
Ie very small portions, or maximimum twice a week. If you give extra e-vitamin, may be somewhat more often.
AS Stefan says, tuna (as sold for humans) s not good in large quantities, for the reasons stated. But as an occasional treat, or to get a sick cat eating (they love the smell) it is very useful. But never give the versions in oil or with salt - buy the all natural version in water, and if you can only get it in brine then wash the salted liquid off first.