The removal of breast

Like, I'm writing a screen where a fmc got slammed in a boob REAL HARD to the point of mutilation during a fight with monsters. Now I have to find a way to process with the removal of that boob.

She is in a wilderness with some medical tools, pills, painkillers, disinfectant, etc. I have tried to make her cut off her boob using her sword that got heated by flame so that she can close the wound, too. But I think that's too wrong medically? But I also don't think she can perform a breast surgery like a doctor. I searched on how to heal such wound on your own but the only option is to pass away.

She also has a twin sister by her side. They are around 16-17. This is a fantasy Chinese cultivation setting, and they are kinda strong so I don't think it need to be 100% correct like real life in term of body endurance or medical advancement?

What should I do in this setting?

P/s: I wrote that the force is strong enough to crackle her rib, not a big one though.