How to not fear that she'll abandon me if she dates?

ok so this might seem lame but I am really struggling with it…I grew up in an abusive household which is one of the causes for my anorexia that I have had since I was 12. I was in the fostor care system from 14-17 1/2 then in and out of the hospital for my eating disorder and my last serious ER visit resulted in me ending up in inpatient treatment for seven months. when I got out of treatment I was blessed with a lady that was willing to help me out, knowing that I could not go back “home”. I have been with her for a year now and our relationship has grown and she is the first adult I have ever trusted and I look at her as if she were my mom. and she has said that she looks at me as her daughter. she is really amazing and the question I have is that I know she wants to get date and get married someday, which she has talked to me about and has said that no matter what I would always be a part of her family, but I cant help but feel really scared that I will lose her to some guy, and I know im of legal age but im not capable of being completely on my own right now, mostly due to my eating disorder but I want advice on how to not personalize my mom’s wanting to date and marry somebody, and how to not feel rejected. her and I have only talked about it a handful of times and I always end up getting angry as a defense and thought I would try to be genuine on here and ask for help with this situation. sorry its so long…