Hi ruderedhead. Welcome to the forum.
You need to be more cunning if you want to talk to JWs. You have to get your message in while their guard is down.
Everything the WT told you from the platform about how to identify and avoid apostates was being listened to by everyone else too, and every time you forget that in a conversation you will put their guard up and the Watchtower wins. That is why I advocate not DAing. It advertises who the 'enemy' is.
To avoid making embarrasing mistakes .... don't make statements, ask questions. That way, if you have a fact wrong, they can't accuse you of lying or deceiving. Ask questions in a way that makes them really want to answer you.
Don't show them opposing literature or websites, instead, ask questions that make them want to research to find an answer.
If you must show them something, make it something they trust. WT literature, dictionaries, books quoted by the WT, anything on their own bookshelf or WTCD.
... and don't inundate them. Just pick one subject that is important to THEM and stick with it. No distractions.
If your friend will still talk to you, practice a bit of shut up. Make her do the talking. Don't even read her a scripture or a passage out of a WT. Ask her to read it to you. Don't explain it to her. Ask her to explain it to you. Ask questions to get her to realise she is using double standards, faulty logic, psychological abuse, whatever. You cannot afford to make any more mistakes. She will just use them as excuses to trash your character to let herself off confronting the truth about The Truth.
Good luck
Chris