"I did mention that I'm mono and if emotions got involved that could get complicated, she said if that happened we'd have to have a long talk."
Do you think it might be possible she thought you meant that as a mono-oriented guy it would be her relationship with her primary partner which would complicate emotions? It may be she was misunderstanding why you were making the comment. Or not. I wasn't there...
I can see your point about jumping in with questions before the friendship is even fledged, let alone before it takes wing. Your judgment is best.
Imagining how it might be... It's hard to know how that relates to reality, isn't it? I think that in fantasies our emotions are under control but in the real world they do not stay under our thumb.
So that you can imagine being in a poly relationship is a sign that it might
be possible for you. But if the situation becomes real, then emotions you had not imagined may appear. Or you may find that the relationships feel natural and normal. I suppose no one can guess how your shoes will fit. You are the only one to know.