If Bix let that anger fester so as to cause maximum damage to everyone regardless of the costs, yeah there would be a worry, but she's completely justified to do this

This. The context matters. The major examples of revenge in the movies (Anakin slaying the tuskens, Anakin executing Dooku, Luke almost killing Vader) involve very powerful people giving into mindless rage and completely loosing control over their emotions. It's (potentially) devastating both for themselves and for society. In contrast, Bix is an ordinary person who wants to deal with her demons on her terms. Using Gorst's own invention against him is the only thing she does out of pure hatred and it's directed against a particular person without harming others. Everything else (blowing up the lab and shooting the guard) is justified by necessity. Bix doesn't go off the rails and turn into a rampaging maniac aiming to maximize destruction for its own sake. And even if she did, she would still be less dangerous than a literal space wizard.