Treated animal fiber shrink?

Hi everyone !
My brilliant student has almost finisher her first hat. She’s afraid it may be to long and is hoping to shrink it in the wash. I think what she is using is a treated animal fiber. That won’t shrink will it?

If it’s treated to be machine washable, then it isn’t supposed to shrink.

We bought it at a small LYS. The label doesnt’ say anything about what it actually is but the person said that it wouldn’t felt so i assume it’s either acrylic or it’s treated.