Talk to her
I think she likes you. Well, i suggest you talk to her and find out her feelings for you, she would not risk flirting with you in your wife's presence if she did not like you. Ask her whether she is ok with Poly..., if she is ok with it, then go ahead and talk to your wife about it. If she is not ok, then keep it at a friendship level, dont even Flirt.
Am also new to poly, and my bf is married, he opened up to his wife which was so hurting to her but she was so understanding to atleast try the poly relationship. I have a few challenges, but life is an experience, and lets see. maybe we can be happy.
Ask me if you have more questions for me.