Emma’s the one who knows about BTTF, not Hook. She knows not to mess history up. But then she steps on a twig.
They even made a point of having her mention BTTF and Marty McFly, so we know that she knows the movies and is thinking about them. And BTTF isn’t the ONLY story in our world about time travel. It’s a generally known thing, if you go back in time, don’t be seen and don’t change stuff!
Also, Emma knows how to blend into situations. We even saw her do it in 3B when she and Regina were on a stakeout. Remaining unseen is an actual skill she knows about because it’s a sometimes vital part of her job. We saw in the Pilot that she was pretending to be someone she wasn’t (she was even wearing a red dress in public while doing it). She should have thought “gotta find some FTL garb so I don’t stick out” all on her own, because playing the part to fool people is something she’s had to do as part of her job.
Emma possessed the necessary knowledge and tools to survive in FTL without getting herself (or anyone else) into trouble, yet they showed her as being kinda clueless and incompetent and needing all sorts of instruction. The only thing she really should have needed help with was the magical device required to get back, and she did realise that Rumple was the one person she should actually seek out and interact with because he did actually have vital knowhow that she doesn’t have herself.