Hey Bird,
I hope your sister is feeling better. Chemo is no fun, I've witnessed relatives going thru that.
I've never tried a vape, but I hear good things about them. A bong would filter the smoke some. I'm sure a cigarette filter would do the same thing for herb as it does for tobacco, but I'm not sure how you would make it work.
I am currently out of herb, which sucks. I sure could use some on this rainy Saturday.