I don't know if its the best thing that you consider your wife an outside party. Also, you say you got into poly because you didn't like feeling trapped. Why did you feel trapped to begin with? Maybe you need to consider the idea of feeling trapped and why it occurred and remedy that before proceeding.
If you love your wife and this hurts her you may need to examine why. Is it just this one person? Have you been in relationships like this before? Does she have any logic to support her argument? Are you sure your wife is poly or just agreed to it so that you wouldn't feel so trapped?
LadySFI- me; Pansexual, Heteromantic, Poly. "Open, but not looking".
C-Boyfriend - Pansexual, Heteromantic, Poly. "Open, but not looking".
Courage isn't the absence of fear, but the judgement that something else is more important than fear. -Ambrose Redmoon