Unfortunately for both of them, the cobra dragon resisted too much and allowed Loki to get into its body. So when the frilled dragon cut off the cobra dragon's head, it didn't help to free it from Loki.
Now the cobra dragon had two choices to make. It could either give up on its head, which will do nothing to save it from Loki, or give up on the rest of its body.
If it gives up on its entire body, it would surely be free from Loki. But the loss of the whole body would exacerbate its injuries and make it worse.
The cobra dragon didn't know what to do, but the frilled dragon had already made a decision. The water blades had now turned on the cobra dragon's body and were trying to chop it in half.
This angered the cobra dragon, because it felt that the frilled dragon was harming it far more than Loki was. This wasn't true, of course.
