"Tug-of-war" 

Michael's own holy energy was restricted inside Ainsley's body and because the body had an extreme dark camp's bloodline, instead of getting purified by Michael's own holy energy, Ainsley's bloodline started to corrode Michael's holy energy. 

Back then, Michael's holy energy could purify Ainsley's cells and make her suffer, but that was when Michael had a suitable medium. 

Now, he was clinging to Ainsley, and no matter what, his holy energy could not really kill Ainsley's body within seconds. 

Not to mention that Michael's purpose was Ainsley's body and Ainsley's own consciousness because he required a living medium, not a corpse. 

This is why Michael was restricted again and again, and he couldn't rashly kill Ainsley. 

However, Ainsley didn't have the same concern, and she was even happier if Michael died!

Ainsley restrained Michael, making it impossible for the archangel to care about Blaze and the Holy Phoenix.