There should be step-by-step instructions with each video, either in the video itself (at the end), or in a pinned comment under the video. They should also all be fairly accurate? There were some small changes to the game after her videos were filmed, so there may be some extra steps now that aren't in her walkthroughs, but nothing in them should be *wrong*
Is there a particular route you're missing? I have some old text walkthroughs for James and the secret route I made for myself for testing, but they too are probably slightly inaccurate at this point. (But I'm happy to share either of those given YAGS is pretty old at this point.)