It doesn't matter if it is unintentional manipulation. It is manipulation that she is doing no work to stop doing. She is doing it, having it pointed out, and then doubling down. If you stay with her, this is going to be your life. You are going to get upset at something she did, she is going to try to manipulate her way out of the consequences rather than apologize and try to do better, and you are going to be hurt. She sees nothing wrong with this cycle except the part where she isn't getting what she wants. This is not a good life for you to try living.
It's not you and it's not your weight. Stop trying to find ways to blame yourself.
I was going to say he was asexual or had some sort of trauma in his past, but now I'm thinking gay.
It doesn't matter if it is unintentional manipulation. It is manipulation that she is doing no work to stop doing. She is doing it, having it pointed out, and then doubling down. If you stay with her, this is going to be your life. You are going to get upset at something she did, she is going to try to manipulate her way out of the consequences rather than apologize and try to do better, and you are going to be hurt. She sees nothing wrong with this cycle except the part where she isn't getting what she wants. This is not a good life for you to try living.
Everything I said can be applied to the other gender as well. So, it's on him to make you feel wanted and desired then. Go talk to him.