If you go back with your friend, make sure they know that you're going for them and that you do not support anything related to JWs. Otherwise, as others have stated, they may take your presence as your endorsement of JW things.
If you can't be that open with your friend because she may shut you out, I'd make sure to point out the logical errors in the WTs and talks during the meeting. This may help your friend start thinking. If someone says that the world conditions are getting worse, google it and show your friend how conditions are actually improving.
If you really believe you can help your friend, it would be worth it. Just don't get sucked in or cause yourself too much mental stress.