I think another thing to consider is the care Karen would receive from the Chee.
Obviously, they could provide for her basic needs, entertainment, education, food, shelter, etc.
But if anything were to go wrong, she was pretty much dead. (Then again, this is according to book 29, and if we want to pick and choose which books we deem "Cannon," I am not sure this argument could work.) Erek stated that there were no Chee capable of performing brain surgery on Ax, and there was no mention of Chee capable of being doctors in the other books. If she were to get moderately to seriously sick/injured, they couldn't take her to a hospital.
It's easy to say that nothing would likely happen, but the likely hood of something happening, I think, is very high. Most diseases are mild because doctors are able to prescribe/use fixes that come easily to them, prescriptions, surgeries, etc. When we lack that, simple things like bronchitis or even a dog bite are easily fatal.