Obviously, Stefan working to find a cure behind Elena's back is beyond gross, as it violates Elena's agency and self-determination, as well as puts her in danger of being a bloodbag for Klaus again while also forcing normative expectations on Elena's future as mother/wife/buried-by-Stefan's-side future. And Damon going along with Stefan and also not talking to Elena about her wishes, but being more concerned with why Stefan wants this? Gross. It's all massive appropriation issues and a violation of Elena's autonomy. Salvabros need to take a fucking seat.
The bright side, however, is that the roadmap to the cure is now secretly revealing itself on Jeremy's body. Like Connor, presumably no one else can see it. So this cuts Stefan and Damon off from this secret knowledge. Let's also not forget that Elena just viscerally claimed Jeremy as hers in "The Killer". Jeremy is Elena's last tie to humanity, he's what's keeping her together emotionally, but now he's also her key to a literal hope for human restoration. If she chooses it. And it will be her choice because it's being held within Jeremy's body now, that very same body being written over by tattoos the way Elena's rewritten his mind in order to protect him (problematic, yes, but it sets the stage for the power dynamic -- all these vampires want to control Elena's body, meanwhile she's controlling Jeremy who's become the symbolic manifestation of her humanity).
Jeremy holds the secret to the cure now and Jeremy is Elena's. No ifs, ands, or buts. So the Salvabros might try to hijack shit, but she'll fight them with all that she has because the key to her humanity is now embodied in Jeremy, literally, and she'll go to the wall for him without hesitation. She's dangerous now.
So we have the foundation for Elena fighting for her humanity, reclaiming it violently and viciously, because it's hers goddammit and nobody messes with her brother or she'll rip your throat out.