There were many factors that deteriorated our relationship and I think living together made things less special and caused her to feel stuck as well. Well, as you have said many experience similar- live and learn I suppose.
I think the cause of the dissolving nature of relationships is quite often, if not mostly, because of a lack of common interests. People stay together because of physical attraction for a time. Although it is very difficult to maintain relationships that have no common spiritual affinities....and it is usually self defeating. When people are younger souls they do not always understand the spiritual questions, experiences and aspirations of older souls. As a consequence, they are often taken from our lives so that we can progress without their hindering energy. This does not preclude the fact that we have feelings for them. But often we find they themselves do not carry lasting affections and lack a development of the heart chakra.