I think she went back in case his body was in fatal danger...
It's not the same thing but if my sister was in danger and I had the ability to heal her, even if that would also put me in danger, I'd go back and do my best to save her because if I didn't I'd feel regretful if something happened to her.
Well we all have different opinions but in my point of view, I can understand her. Sure it may be infuriating to the ml but if my lover is also on a battle that I know he could die or be on the verge of death then I'll probably go there too. Then I'll have no regrets whatever outcome it may be
Another scenario is like when she gets there and the battle was already over then she could heal him right away.
In stories like these its good to use your logic, but sometimes the heart needs to be followed u know?
I really thank the translator for translating this, but omg the actual manhwa is so infuriating. GURL I DON'T UNDERSTAND WHY WOULD YOU COME BACK TO THE FIGHT IF YOU CAN'T EVEN FIGHT AND WOULD JUST BE A BURDEN LIKE? "I CAN'T LEAVE HIM" you being there would just hinder him because others would then target you WHICH HE WAS TRYING TO PROTECT SKFJKEKDJ and also ml fell in love too easily too. It might still pass as a good read for others but honestly I can't read shit like this anymore lol as long as the fl is being annoying