The answer was right in front of us all along: in order to overpower Kryptonite, just endure dealing with it for 15 years and you can break free.
It appears that Kara has developed a tolerance for the pain/weakness brought on by Kryptonite. Which is understandable and believable. To use an analogy, it would be that Kryptonite is like a mortal gunshot wound. It's going to kill you, but if you've been shot before or exposed to that level of pain often enough, you can power through it.
I'm also assuming there was Kryptonite in the bullet too...
I liked this episode. I'm okay if Supergirl isn't the main character for every scene, just as long as it's the majority. The adoption plot was nicely placed, as that led in to Kara's adoption and then Alex breaking through the mental blocks - and three
very nicely done emotional scenes.
I swear they can could be crying for the entire episode and I'd be spellbound! (I'd probably start crying too...)
Lockwood has also had his neatly-ordered little world up-ended, in finding out that he's just been a tool. And it is also nice to know that 'Jimmy' will not be keeping his powers! Huzzah!!
Lena with Lillian were really good scenes. I liked that Lena urged Lillian to still drink the potion, leaving the idea there that she really did poison her mother.
As to the fight scene, I was alright with it. I wish they had not used the helmet, as it shouldn't be all that hard or expensive to have two people in the same scene with the same face these days. As to Supergirl losing the fight, that must have had something to do with the new power Red Daughter has. I hope we get a good explanation for it, though it's probably just an aberration in the cloning brought about by the Harun-el.
My one critique would be, what
the hell happened to the sun!? RD hit her with that new power, zinged her into the air and it was just suddenly nighttime? Talk about 'knocking her lights out!'
I can see that it must have been for the absorbtion scene with the plants, but it would have been just as easy as having those scenes happen at night rather than day.
Someone had to make the ham-fisteded decision to just make it night time between one second and the next in order to fit that scene.
Which I was okay with. Obviously drawing stored solar energy from plants wouldn't be enough to fully power her, but give her a little
kick to keep going, sure. The 'light worms' that they used to depict it could have been changed to a building aura of light coming up from all the plants and converging on her, but what they chose is not a deal-breaker.
Now I need to know what drew RD away at the end? She heard something, said 'No!' and flew away. I don't think she's dead though, as that would be
too cumbersome a way to end the character. She'll turn up again, and I hope she's not destroyed. I think the boy will be important in turning her around and at least getting her to stop fighting.
How I would like them to end it would be to have her go to Kandor, to be with their mother and Clark.