How do I stop my daughter from seeing what’s on my browser through Family Sharing

Not sure what you did, but Family Sharing does not work like that.

The only way she would be seeing what you browse and you seeing what she browses, is if you signed in to your own Apple ID on her devices and have iCloud tabs enabled on her device. This should not be done of course as it shares more4 than just browsing history.

Signing in to the same Apple ID on devices used by different people entirely defeats Family Sharing. Basically doing this completely bypasses Family Sharing.

You can enable Parental Restrictions to limit what kind of websites can be opened on her device however

click here ➜ Use parental controls on your child's iPhone and iPad - Apple Support

To view visited websites, you can then access Screen Time, then tap on your child's name, and the on "See All App & Website activity".

Each person in family sharing should have their own Apple ID and be logged in with it on their own devices. Apple IDs should absolutely not be shared.

Does she have access to your Apple ID? If two devices are both logged into the same Apple ID, the browsing history, frequently visited websites etc. are all visible on both devices.