I believe Abigail makes a comment on how Veronica will flee as soon as she hears about her (Abigail) being arrested. She was still on the cruise ship when Columbo took Abigail off and Columbo at that point had no reason to detain Veronica as a material witness.
Edna's brother promises not to make trouble if Columbo lets him go with him to see Tommy, but then as soon as Tommy says a word to him he punches him out.