Seriously, Lena being deeply hurt by Kara & Cie's lies/general behaviour, alright, but they pushed to far her reaction to excess of zeal, which borders on the Luthor's madness/resentment. I mean, that she feels humiliated and she decides to teach her supposed friends a lesson (the type of regardless I forgive you, my trust and confidence will be no longer blind and total), it would be understandable and maybe even shared by a majority of viewers but at one point, it is therefore necessary to know how and when to whistle the end of the game. Alas, again, Supergirl's writers showed how much they were unable to show moderation.
Result: they completly ruin Lena's character they have made 4 years to build (though she is a brilliant and endearing individual, she remains someone very sensitive who tends to let herself be deceived by her emotions too, in particular in her will to do too well). Instead, since the beginning of s5, we had a Lena cold/calculating who does not hesitate to use others to get what she wants and worst, who has the spiteful grudge, even for those
who like me, like her since s2 and believe me, It hurts my little heart
to write that! It is like Lex Luthor, who was fascinating in the 4B but now, in 5B, it's indigestion
Frankly, to correct the mess writers created (and proudly supported by producers) since the beginning of s5 with their "battle for Lena's soul" (that being said, I don't really have the feeling that so far, Kara and her Superfriends really took this cause to heart and work hard to reach this goal so much they were busy to self-flogging aka Kara and/or to continue their business as if nothing had happened, turning completly their backs on one of their friends who seems upset and emotionally lost aka the other Superfriends -> Brainy would have been the 1st to understand Lena's position, especially after his little speech about the difficulty to trust again and use of boxes to lock up emotions in S4) they will need to be very imaginative to correct the badly creative Lena's storyline to make her become likeable again (I don't think their intention was to make Lena unbearable to fans but they managed to do it and I don't think either their intention is to copy Superman vs Lex's tense relationship and besides, we already know that Lena won't turn villian so...), maybe in letting J'onn finally erases her short term memory or a sudden amnesia due to a head injury or whatever, will allow to correct the situation... .. I know it is stupid scenario and why do it now when they could have done it after Crisis events. I'd answer to that,in saying they try to dismiss the ease of the loss of memory, which was an easy scebario to develop their storyline of betrayal and its consequences, but they ended up getting in a complete muddle and making the plotline last unnecessarily and going to far in Lena's loss of sense of reality. In the same time. I fear that keeping letting Lena pursue her project until she realizes that she is falling on the wrong side of the barrier and that she decides afterwards to recover in changing her stand, finishes to be awkward and worst, this total change in attitude will not erase what she has done since the 5x01 to 5x100 (even if it is clear that Kara's caution in 5x100, will serve as a wake up for Lena ... even if we will have to wait a little longer to really see a change in her). And now, 7 episodes remain to try to correct the situation. Even if for CW, ratings are satisfactory, they are nontheless declining and I won't be surprised that this decline was facilitated by Lena's messy storyline. That being said - but maybe I'm wrong - I still don't think that killing-off Lena Luthor will be solution, as an eventual sacrifice for a good cause, in 5x20, the last episode of the current season. It would be too simple ... and sad, especially after 5 sesons. But I know, some of you will say that Arrowverse producers/writers already killed popular characters in the past, often becasue they thought their stories were over.... Anyway, a quick redemption on 1 or 2 epsiodes, as seeing as they intend to pursue Lena's mental crisis as late as possible, followed by a potential death of the young Luthor would be strange and maybe too much (even if in DC comics, she dies after being seriously injured by her brother). Arrowverse series already demonstrated that they don't necessarily follow comics so, everything is possible.