How to protect one's privacy while sharing Wifi with a controlling and tech savy partner

Not sure if this is the right sub to post this.

Also I'm aware we're not allowed to talk about VP\*s here and I have a feeling that's the answer to what I am looking for.

Moving forward to my question:

Consider this scenario: Controlling partner with an history of snooping into his girlfriend's phone is much tech savier than his girlfriend. They live under the same roof and use the same wifi. How can the girlfriend protect herself / …

partner privacy protect sharing tech wifi