I guess I don't understand what they should do differently, if they have current lesbian characters? Though the original point was just to show that there are other shows other than the 100 with well written lesbian characters. Really, of those shows, the only lesbian deaths I can remember were Maya on PLL, which had a reason in the story, and Sarah on Arrow and she came back to life.
One big issue from what I've seen is that if someone wants to watch a show without a lesbian character dying, there aren't many options. Even in the 100, the main character is still bisexual, but still, the lesbian character's death spread the notion that lesbians don't get happy ending, and neither does her bi girlfriend. It sorta goes hand in hand because even if there is still a gay character on the show, killing their significant other sends the message regardless. There are other shows with lesbians character, yes, but few have characters that are not stereotypes, even fewer have a happy ending. It's not about the ship ending up together either, it's just about showing that lesbians can get a happy ending too. Buffy and the 100 had some of the best written lesbian characters, but yes you are right, there are others, I just meant it's hard to turn to a different show where we won't witness a lesbian dying.
As for the death on those shows, Maya and Shana died on PLL (both were POC and lesbian), Nadia in Lost Girl, Alisha in the Walking Dead. As for Sarah I had no idea she came back to life. Here's a list of characters that died on different shows
The 35 Most Horrifying Lesbian/Bi Character Deaths on Television - AfterEllen. That makes 35 lesbian/bi character that are dead (and there are more). Overall, the total amount of lesbian/bi characters make up for maybe double that number. Which means gay characters have a much higher death percentage than straight characters, hence the dead lesbian trope.