I would say every kitty is different and requires different frequencies of bathing. If yours is not oily or dirty, then best to not wash, otherwise it will dry out the skin. You'll just need to learn your little ones body over time and you'll come to learn how often she requires bathing.
I agree with Jacksmom. As time goes on you will know your kitty better. Since she has been with you a week, you could give her a bath and see what she looks and feels like after waitign 1 week. Next time you can wait 2 weeks and compare the results.
My early boys were greasy enough after a week to leave smudges on window sills, heater covers, and on light colored laundry. The marks should wash out with regular detergent and warm water, but you could pretreat with a stain remover or add a scoop of a laundry booster to the load.