There are a lot of people who have experienced this similar thing. It seems very common that a unicorn exists for a short time when the passion is high; the NRE is going on... and then a change occurs and either the unicorn ends up favouring one over the other or wants another partner or moves on entirely.
It is hard I'm sure. It is possible to sustain this type of relationship if there is a mass of open honest communication and a lot of process. If that feeling you have doesn't go away for either of you then maybe you should approach her again and see if she wants to negotiate some boundaries now that the NRE of your relationship is over and a "settling into it" is starting to occur. Relationships change and grow, its a matter of whether or not you want to change and grow with them and can stomach the jealousy and other uncomfortablnesses to allow that change to become something that works for you all.
Take a look on this forum by doing a search for tag (such as "unicorn" and "NRE"
) or for similar threads. There is a lot of support just by reading similar stories sometimes and perhaps that will help. you are not alone...