Hi and welcome,
If you just went through a rocky patch and are in a recovery mode why not concentrate on that. Regain what was lost and add to. Have you 2 discussed the correlation of the rough patch to the suggesting of opening up the relationship ......and how that could be a insecurity triggering event.
What's your motivation in pushing this now ?
And if she is organically poly this topic will bubble to the surface again anyway. Take a break from these discussions for a while let things cool off, memories fade. Let some time past then broach the topic agin if you feel strongly about .