I am still worried and somehow afraid of the "definitions talk" where she asks me "what are we?" and I don't know how to answer her and she then gives me an ultimatum to decide whether we are in a relationship or not and and.... here goes my brain too far again.
"I am letting myself fall in love with you and watching to see how it happens."
The best way to deal with these conversations is to be absolutely clear in your head and then present that clarity in the kindest way possible. People get hung up on semantics. It comes from a fear of expressing yourself, of making yourself vulnerable. You will find, as you get older, that control in any relationship belongs to the person with the most confidence.
I dated a girl who, by the second date, knew I would be with either for weeks or forever. When she really pissed me off I said to myself "weeks" and moved on.