Delete Messages from iPad and not iPhone

Hello! My wife has an iPad Mini with 16 GB and it’s linked with her iPhone (128 GB). iPad is on iPadOS 13.2.3 and iPhone is on iOS 13.3. We can’t update the iPad because it doesn’t have enough storage. She doesn’t use Messages on her iPad, which has over 4 GB of storage used. We’ve turned it off so it’s not syncing, but we want to delete the conversations from the iPad without deleting them from the iPhone. Unfortunately, the current version of messages doesn’t allow me access without logging in and turning it on again.

What’s the best way to delete the messages from the iPad? Will deleting the app itself work while keeping it on her iPhone?

Thanks!