Losing best friend because of weight

Basically me and my best friend have always been over weight but I have a more round face and body shape so I look a lot bigger than what she is she doesnt look that big at all and has a really pretty face. However I started dieting and I’ve recently lost 3 stone which I’m proud of so I’m happy with my figure now but whenever I ask my friend to come out she always says no and we got in an argument about it because I felt like she was going against me and she said it’s because I’ve lost weight she said when I was fat she was the prettiest and thinnest and got all the attention but now I’ve lost weight she’s embarrassed to come outside with me because she will be fatter than me. I said what can I do to make you come out with me and she said get fat again. This made me really sad because I worked really hard and she knew how depressed and self conscious I was when I was fat and I feel like she has been using me all this time because I was uglier than her to make her self look better. We also have a holiday together in October and she’s saying that she isn’t coming with me anymore. My family and other friends always told me she was a fake friend and always treated me like shit I just never really noticed it until now and I don’t know what to do about it I can’t imagine my life without her in it :(