I need some solid wise advice guys?

I have a toxic colleague who’s always complaining about our senior. Our senior is lazy but instead of saying it to him she’s CONSTANTLY complains to us. I’ve advised her to talk to him about it since the rest of the team address issues with him. She tells on the rest of the team trying to turn him against them and kisses his ass to his face. But the minute another team member said tell him your concerns, or I’ll ask him to help you if you like, she became excessively offended and told the colleague to fuck off. What on earth is that about?

I need some solid wise advice guys?
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