They had been dating for 3 whole years and living together for 1 year without telling the other she loves her? It even goes so far that her partner begins doubting their relationship...
Nice with a happy ending (if a bit rushed) but these kinds of stories just feels like contrived drama.
There are plenty of reasons someone can end up closing themselves off: autism, demisexual, social anxiety, an abusive upbringing, previous relationship gone horrible, etc.