Firefox focus browser

If she uses Safari, there are some good plugins. Not all are free. StopTheMadness Pro is not cheap but is a solution for many annoyances, not just YT. UnTrap for YouTube allows you to hide many elements like shorts. And SponsorBlock automatically skips sponsored segments. If she uses the YouTube app, delete it and set up a shortcut on the home screen to open the web version instead.

DuckDuckGo’s web browser blocks YouTube ads for me on iOS

LibreWolf browser (Firefox fork) also blocks YT ads pretty well. I use it at work to listen to music when focusing on programming.

YouTube Premium is like 2 usd a month via India, or 4 bucks for a family account.

Just create an Indian Apple Account (find an Indian address via Google Maps, phone number can be from any country so can just use your actual phone number) buy Rupees for the AppStore via https://www.amazon.in/apay/detail/apple-store-codes

Log out of “Media and Purchases” in the iOS settings under your account. Login “Media and Purchases” with the Indian account, redeem your Apple Rupees in the App Store, go to YouTube app and subscribe. In the subscriptions section of the iOS settings you can upgrade or downgrade the subscription if necessary.

With Signulous you can side load uYouEnhanced. This blocks ads, includes SponsorBlock, and a number of other nice add-ons. Signulous costs $20 a year though, and you have to install a sketchy certificate to side load, and there's always a chance Apple breaks Signulous (happened a few times before but there's always been fixes). You can manually side load uYouEnhanced without Signulous, but it requires some research & weekly upkeep.