I have complicated feelings about the last chapter, I expected a complete catharsis after what happened, and well, it kinda is, but I'm still not satisfied.
But I would say that it is more of a happy ending than a sad one, you can see on page 118 that the black-haired girl is crying, she is sad about what she did. About Angela she will never forget what her lover did to her and if her wings grow back, she won't let her cut them off again, but she will take her along with her (page 131 and 132).
Unfortunately, if someone wants to grow, they have to fail or suffer, and we see that both characters go through this.
Besides if we look at the art, it looks so paceful and beautiful in the last pages, I think the author wants to give us an optimistic feeling about this ending.
Honestly, I would say that if you're in a toxic relationship you should break up with your partner inmediatly, but this story seems to be about a toxic couple that stabilizes after all that chaos.
So far I am in love with Murasakino, each of her stories are different
P.D: And I have a feeling that Angela will grow wings again, look at pages 134 and 135, we can see the feathers and we see Angela's back and behind her there are birds flying. Why would the author give us false hope about mentioning it?