Definition of "childishly"

I knew, of course, it was but an innocent game on her part, a bit of backfisch foolery in imitation of some simulacrum of fake romance, and since (as the psychotherapist, as well as the rapist, will tell you) the limits and rules of such girlish games are fluid, or at least too childishly subtle for the senior partner to grasp—I was dreadfully afraid I might go too far and cause her to start back in revulsion and terror.

1955, Vladimir Nabokov, Lolita, 1st American edition, New York, N.Y.: G[eorge] P[almer] Putnam’s Sons, published August 1958, part 1, page 115