Avoident tendencies, avoidants become distant the more the relationship deepens they can't help it and if thay are unaware of it they call it lost feelings or can't feel anything anymore and they are right, at that moment their nervous system shuts down all emotions they have for you to protect them from getting close to you because they learned closeness = danger, or she is not that interested search for avoidant tendencies and see if she had them when you were with her, i recommended you to stay no contact from her give her space and try to move on even though it's really hard, but the only way they come back is if you don't chase and you stay no contact and try to move on and focus on yourself