You sprinkle hints at earlier episodes that Simmons might be inclined to react that way. As it sits, Simmons has been exposed to super powers many times and has even very nearly died from contact with alien tech and she never leaned towards developing mutantophobia even a little bit. That makes it seems a little bit contrived that her stance now changed by events that were not really different in magnitude, but merely in results.
When Simmons tried to kill herself would have been a great opprtunity to show or at least have the character develop mutantphobia. Instead as long as bad stuff happened to strangers. She was good. Once someone who she was close to and had feelings for died. Then the mutantphobia suddenly is part of her character. Mind you in a world where there is people with powers both mutant and non-mutant. Targeting mutants makes little sense imo. Human Torch, Black Panther and Iceman. The first two get a free pass on racism. Iceman gets persecuted. It's not like mutants and non-mutants have a tattoo on their forehead that make them stand out. If Marvel really wanted to show racism properly then the fear would not be towards Inhumans and/or mutants. It would be against everyone and anyone who had superpowers mutant or not.