They aren't really coming to see if you're a good parent, as R said, they are obviously trained to look for vulnerability, PND, that sort of thing.
I suspect you have one coming before the babies are born since you're having twins? I never met either of mine until after the boys were born.
Some HVs are great, they are very supportive and pleasant to be around. Others may be more abrasive with more fixed views about child-rearing. When Jake, my youngest, was born, I had a rotation of them coming because I had some issues with my c-sec scar... I hated one, thought one was a ding bat, and liked the third!
Don't sweat about it. IME, there is usually a team of them so if you don't like one, you don't have to see her. And after a little while, you'll probably find that they have a place (a drop in clinic at the surgery or local church) where you can go rather than them coming to you.