Two thoughts occur to me in reading your post. First (and this thought is a question), is Cherry unhappy with your being polyamorous? Is she accepting of your polyamorous nature?
Second (Hey, another question!), is she aware that people can start out in life mono and change over time to poly? (Not that she should have to do so, or that she needs to change. Rather, is she aware that people change in this way sometimes? [I did, for example]).