Susan is about 1:8 scale, while Jay is 1:12.
Some wondered if it was Susan's halo that made the "clang" noise after the previous comic. Honestly, I'm not sure myself the physicality of the halo.
For comedic purposes, I've had it interact with what it touches, but I don't think there's much in the way of tangible mass to it. I think it will essentially just move out of the way of whatever touches it without much force, while always returning to Susan.
Ultimately, though, the rules of how it work at any given moment are governed by what I personally find amusing, hence how it's wound up on the floor.