Honestly I love the idea of cook reader interacting with some of the dragon ball villains. Like I just love to imagine frieza getting hit with a spatula for one reason or another

Yeah, that would be hilarious but I think that it would take some time for Cook!Reader to establish some sort of middle ground between them in order to get away with the bullshit they usually do. But at the same time like I've written before, Cook!Reader doesn't really care much for anything apart from cooking. (except for their friends and family)

Once Frieza realize that Cook!Reader is the only who can cook him his favorite dishes, he would let them get away with almost anything. Murder, arsonism and even letting them boss him around. But at the same time, Frieza might consider kidnapping and enslaving Cook!Reader just cuz he's a selfish spoiled brat. Luckily for Cook!Reader, they have bodyguards who follow them around and they would probably enjoy criticism to further develop their cooking.

Relationship between Cook!Reader and Frieza would mostly be like between a parent and their spawn. Frieza would be off enslaving planets and Cook!Reader would ask him to bring them some ingredients from it or the alien would mostly keep some planets for Cook!Reader to farm. Cook!Reader would probably propose a nice comfy planet to Chi-Chi to live in and grow their veggies and fruit.

Frieza would have a bad day and his minions would send Cook!Reader his way offering him some chicken nuggets fresh from the oven.

Compared to the other characters of dragon ball, Frieza doesn't have a huge appetite but he would always feel guilty whenever he comes back from a trip where Cook!Reader would offer to cook for him and he wouldn't dare to tell them that he already ate on the way back. So Frieza would mostly try to eat less whenever he came back home not to confront Cook!Reader's sad face.