Same with me. Only my situation was worse - there was a kid involved. Five years, three of which we were engaged in. And a 1 year old girl.
She slept with two guys, who I won't really call friends, but I knew them. When I found this out, I couldn't kick her out immediately because I thought of "my" kid so I took her for a paternity test.
During this time she was staying with a friend.
When the results came back negative, I immediately went to buy the cheapest schittiest suitcases and packed all her **** and booked her an Intercape ticket to leave the next morning (she was from a different province). Whatever couldn't fit, I threw in the garbage bin. I took the suitcases and results to her at thhe friends place, rang the doorbell and left the results on top of one of the bags.
I have never seen her again after that.