How do I help my girlfriend

My (CisF) girlfriend has been dating me for over a year. She’s always considered herself closely tied to loving women and being sapphic, as the beginning of our relationship was this. She worries that she might not be attracted to me once I follow through with transitioning (Start t, top surgery, etc). She has struggled grasping the idea of this ever since I came out. We both love each other so much and she is extremely attracted to me now while i’m pre transition. It eats her alive and makes her feel like shit so I’m just wondering if anyone has any advice for us.