I'd say just apologize to each other, have a discussion over what happened and what to do next time, and move on.

As for the "do whatever you want", try to say something else like, "would you feel happy if you did it?" Or "I'm glad you value my opinion. Personally I would". If you say something like "you should do what you want", it could be taken as a tad dismissive. She cares about your opinions, so she is asking you. If you put it back on her, that may make her feel like she can't engage with you as much.