Ero-Sage

Pain already fucked up half the village before she even was notified. Its only natural that a medical based Nin would look after the wounded and give them a chance to survive or even rejoin the fight before jumping into battle. She was just following her strengths. She was ready for Pain once he showed up thanks to Kakashi and friends intelligence on his abilities. She would have surely killed Yahiko pain and moved on to the others but Naruto showed up and was way more capable. After all it is the jinkiruki's duty to be the hokage's show of strength and to protect them along with the village.

I completely agree with you (Najiro) about the Sannin showdown and the small gap shown between Kabuto and Tsunadae, however I believe she had a different mentality at that time and employs a more serious and adept mindset now.