Is an actress beyond her "peak" in her 30's

what happens when an actress turns 30? is this really a thing? where an actress's work declines?

Used to be the case but not really anymore- Kriti, Yami, Ileana, Bhumi and many more mainstream heroines are all 30+, not to mention Deepika, Kareena, Katrina. Early 30s seems to be the new mid 20s from what I can see 🤷🏽‍♀️

Not today. Deepika, Kangana, Anushka, Kareena, Katrina, etc. are in their 30s. They're in their peaks. Anushka's case is different. Today, an actress younger than 25 isn't taken seriously as a mainstream lead. It's simply how society has evolved.

Peak years would be 28-35 in Bollywood today.

May be a couple of decades back, but definitely not anymore. Some noteworthy examples cited in above posts.