My ex-boss about to leave the company but recently shit talked about me in a business trip, shall I confront?

My ex-boss (ex because she resigned to move to another country) is about to leave the company for good in about a month. Recently she and some other colleagues went to business trip and I hear she bad mouthed me a lot. I know this is an ongoing issue and she does this about other colleagues too. Shall I confront her and just say "I know that you've been badmouthing about me, disappoinment would be an understatement." I just want to confront her about her behaviour and put her in to her spot somehow.

Would this be a stupid idea?