Need urgent help for legal actions

Hey guys talked to my childhood bsf after like a week( we talk on daily basis and our chat Convo never really ends)this whole week she was very unavailable and lost I knew SMTH was going on w me and today she opened and cried alot because she's undergoing something one should not and I need help from you guys cause I'm unaware of the process in these situations so please help me after reading

She graduated from one of the prestigious IITs and had a group of friends and now everyone of them are placed and doing their jobs and all of them are in good terms with one another too

So recently this one girl from her group started making Instagram videos and started defamation of each one of them by falsely accusing of very absurd reasons and making herself main character like everyone wanted to kiss her take her advantage and girls encouraged that blah blah all of which is a false information and also she is making whole threads about her friends with their full name tagging their instagram handles with all of the fake info and derogatory remarks and ykw she met with her two months ago and they had a great time outing....she and her partner have gone mad and ngl they're posting anything legit anything about each of their friends idk is this about getting viral or getting the frustration out but my friend wants to take legal action and make her payment for her actions please tell me the right way to do it

Any lawyer's or judiciary persons help and advice would be appreciated