A theoretical shared dreaming trigger

My girlfriend and I had the idea to try shared dreaming, and we raised the question - how do we truly know it's us in the dream, and not some subconscious representation of the other person?

We came up with, in the dream, we will tell each other a random word - so when we wake up and say, "did you say, banana?" "Yes, did you say ostentatious?" or something of the sort, we would know it was really us.

What do you think - is this pretty valid? Are there any better ways to know that you're speaking to a shared dreamer instead of a DC?

Because you would have similar/ same parts of the dream, things may seem slightly different depending on what we think something looks like.

I am very curious if you succeed in the experiment.

how bout you try it and tell the results. i thought of this before :P