Even Supergirl’s sister series Arrow embraced this concept when Oliver Queen decided to focus solely on his life as The Arrow in Season 3.
A mentality such as this isn’t necessarily earth shattering within the grand scheme of superhero arcs.
In fact, characters like Batman and Iron Man similarly (and famously) recommitted themselves and doubled down on their slightly obsessive endeavors in the wake of massive personal tragedies.
The difference here is that Kara is often regarded as one of the most incorruptible heroes in the entire Arrow-verse, and her willingness to dive into such a dark character arc should instantly tell us how Kara’s decision to send Mon-El back into space has affected her.