Just be yourself. If she wants to meet you she's already accepted poly and, at the very least, the idea of you. The best thing you can do is be who you are from the start so no one feels surprised or upset if things come out later. Be clear on what you hope to get from this relationship and be willing to listen to what they have to say. Good luck!
I'd rather be hated for who I am than loved for who I am not.