Dakota Fanning is now 23, yet still has the air of a fragile child. And in Ben Lewin’s “Please Stand By,” that sometimes brittle vulnerability serves her well as Wendy, a young woman with autism who dreams of leaving her group home in San Francisco and living with her married sister and baby niece. Yet despite her commitment to the role — and the generally fine supporting performances — this timorous tale sidesteps uncomfortable realities in favor of soothing whimsy and preordained uplift.

There’s nothing wrong with choosing cute over challenging, but it feels condescending to those on the spectrum and insulting to audiences who might prefer not to be cosseted. Wendy herself is a completely credible character: bright and forthright, she holds down a minimum-wage job at Cinnabon and retains an encyclopedic knowledge of “Star Trek.” Observing how the ultrarational Spock processes the emotions of his human colleagues helps her negotiate her own relationships, watched over by her motherly therapist, Scottie (Toni Collette).

The story spun around her, though, is a fairy tale of tentative independence with every edge buffed smooth. Rather than investigate, say, why Scottie’s devotion to her patients seems to have alienated her teenage son — or address the painful realities of protecting infants from tantrum-prone relatives — Michael Golamco’s script (adapted from his one-act play) sends Wendy off on a picaresque journey to Los Angeles. The competition deadline for her original “Star Trek” script is looming and mild misadventures lie in wait.

It’s all very comforting and credulity-testing: even the kindly police officer she encounters (Patton Oswalt) is able to calm her down in Klingon. I’ll leave it to dedicated Trekkers to vouch for his accent, but I think Lieutenant Worf would probably approve.