I get people trying to symbolise the story and give it pretentious meanings, but it's simply abuse. The mc was scared Angela would leave her, so she cut off them wings. That's what abusers in abusive relationships do. Make sure you're totally dependent on them and you are mentally restrained to them.
Angela was fine with it, because she also got too dependent on the mc. She was conflicted between leaving her and staying. Once the mc cut her wings, she had no choice but to stay with her and forgive her. Typical victim. As people have mentioned multiple times before, this is just a case of codependency. It's nice to read all these philosophical explanations, but at the end it's nothing but a relationship between a abuser and a victim; an abusive relationship.
That being said, this was a very interesting story to read and murasakino's art is top notch as always. Probably going to my favourites.