Going just by the opening post, I would worry that she thinks she might be "the one" that makes you become mono with her, especially since you said you might be mono. I would worry that she'd work hard to be "so good he doesn't need anyone else" only to be crushed when you meet someone else, and she thinks she wasn't good enough.
I'd really be worried she'd say "yes" just because your polyamory doesn't seem concrete to her and she can just hope it will never come up. So I would suggest being extremely clear about that.
If she still wants to give it a try (and would be okay with you having other partners) then good, but I would make sure of that first to avoid something messy later on.