A bit of context:
This is an illustration for a Russian-language fanfic about the relationship between Snails and Sunset. It may seem like she beat him up, but she didn’t. Sunset didn’t give him the bruise. Snails got it when he tried to protect her from bullies, even though she didn’t need his help at all. Sunset had previously asked the guy to help her make peace with the mane5, and not wanting to seem weak, she asked him to keep her request a secret. In this scene, she’s angry because she thought Snails told Pinkie Pie everything about her request.