It's a fantastic game.
You are correct about your solution.
Get what you can reach from Sasha's mind now. You will need to go back in later when you have the power of Levitation to be able to reach that rotating mobile and get all of the figments and mental cobwebs in the level.
But you'd be surprised to find out that there are a lot of places that may seem out of reach that you can get to without the power of Levitation. For instance, in the Campgrounds you should be able to reach at least half of the Scavenger Hunt items without the need for Levitation. A good double jump can work wonders in some places. Also, most of the Psi-Cards and Psi-Markers can be reached without Levitation which will give you power-ups sooner rather than later.
This is important because, for instance, once you find half of the Scavenger Hunt list, you get a good power-up from Ranger Cruller and can go into Sasha's mind for the first time at a higher level. It's possible to be at level 24 before going into Sasha's mind for the first time (and you will have the Cobweb Duster, too!).