Can my ferret be pregnant?

I have two girl ferrets and when i went on my hols i took them with me. the owners of the campsite have ferrets also so I put them in with them. They had two boys but the were both done but i'm not sure how so the may still be able to get my girls pregnent.( they may have had a vasectomy that didn't work). The were together only 30 mins max ( i was therebut watching only watching one of the jills) but one of my jills has swelling and keep dragging my other by the neck!!! Can she be pregnet?? or can ferrets like dogs have pretend pregancy?