It is super risky. I saw an article last month that another patient they tried this on died. The problem is the immune system imprints on “self” early in life. Introduce any changes to the genome and every cell that starts cranking out these new “non-self” proteins is suddenly subject to attack by the immune system.

This is exactly what is happening with the covid mRNA jabs, but on a smaller scale.

In OP’s story they must have suppressed this girls immune system for the therapy to take. They might eventually be able to retrain the immune system to change the definition of “self” and not attack the new genome cells. We have a long way to go for these therapies to become mainstream. It’s really cool science and encouraging to think we may one day be able to cure many, many diseases this way.

Of course, it’s far more likely they will use this technology to introduce an ethnically targeted plague.