So am I right in thinking that this DNA family member isn’t related to your childhood but has just crawled out of the woodwork having done an Ancestry DNA or similar, but because of your relationship with your known family you’re not keen on entertaining getting in touch with them?
Not that I’m in any way suggesting you should, FWIW if some randomer crawled out of the woodwork off the back of a DNA test I’d tell them to do one as well, but it sounds as if your friend and her partner are leaning more towards accepting contact from this person because they’re an unknown family member, which is slightly different to encouraging you to get back in touch with the family from your childhood.
They’re still out of order, but there are a lot of people who seem to think that an unknown family member reaching out is something to be explored, and I am certain that if you posted here that you’d had contact off the back of a DNA test, without mentioning your childhood, there would be plenty of people on here who would encourage you to make contact.
You don’t have to have contact with this person, but equally they may have no involvement with the family in question, and have no idea of what kind of childhood you went through.
So I’d would make it clear that you’re not going to get in touch with them and that’s the end of it, but I’d think about whether you want to end a friendship off the back of it, because it doesn’t sound as if they’re wanting you to develop relationships with your abusers, just with an unknown family member who probably doesn’t even know anything about what you went through.