It's amazing how little fact-checking some of these entertainment news outlets actually do.
The DC Daily video in question was released in February of 2019 at https://www.youtube.com/watch?v=bMOSyDE4YX0
Conor Leslie's minor comment was in no way a giveaway if you watch the entire clip and get the entire context.
I don't know when production of the finale happened, but based on the full video, it is highly unlikely that Leslie hinted at a return as reported by the Brazilian tweet, CBR and other sites.
In the books, Donna did not have to die to become Troia. She only became Troia because her Wonder Girl history ("Who is Donna Troy?") got screwed up after CRISIS because Diana reached Patriarch's World well after the Teen Titans began.
In YJ, the showrunner posted somewhere that Donna joined and quit the team during the break between Seasons 2 and 3 to become a UN ambassador. No indication that the YJ Donna died. In fact, Diana calls her "Troia" or "Sister." Not sure if Donna is even the character's given name in YJ. Seems like Troia is.
Not sure how it compares to the other Infected/Secret Six one-shots, but Deathbringer didn't do much for me. It had more of a Titans focus than just on Donna. And, well, it's lackluster. None of the characters come across as competent or interesting. There's a rehash of Donna's convoluted history and no clear reason for why she was identified to be one of the Secret Six.
If you're a Donna fan, not worth the read.
And, on the whole, I'm tired of the Batman Who Laughs.
That's another issue: which version of Troia is coming back assuming she is? The post-CRISIS Troia with the uber convoluted backstory? Or the killer Troia designed and created by Derinoe to kill Diana?
This may be the rare case where it's better not to use the source material given how such material is a hot mess to begin with. Donna Troy is that rare case because of the upheaval of her origins thanks to CRISIS, her incarnation as powerless human, a Darkstar, good Troia who died because of that Superman android but suffered in a thousand lifetimes thanks to John Byrne's Dark Angel, and then The New 52/Rebirth version that's currently in the DCU.
I hope, with all the sensibilities the Titans TV show writers/creators used to decide on a simplified origin for Donna in season 1, they'll do something similar for her Troia rebirth/resurrection/transfiguration.
With Donna's body being returned to the Amazons, it could be as easy/simple as the Purple Healing Ray and a name change.
Or... something less boring.
I made an OC named Tanya Wilson who borrowed several aspect's of Donna Troy's demi-titan origin. Tanya realizes she has powers as a teen, does superhero stuff, gets into a fight with Trigon and ends up with several broken bones. When the Amazons try to use the Purple Ray, it doesn't work. Instead of healing her it starts ripping the skin off her leg. Why? Because it was made by the gods and doesn't heal titans. So she goes outside and lays on the ground and passes out cold. Has a chat with her titan parent(in Tanya's case it's Gaea), and wakes up fully healed... and also since she now understands her powers better she can do stuff she didn't know she could do before.
I like the demi-titan origin because it's interesting and unique.
Lilith Clay AKA Omen a member of the original Teen Titans and who first appeared in TT #25 way back in 1970. In New Teen Titans, Wolfman gave her a Titans origin as the daughter of Thia, the Titan goddess of the sun. She left the NTT for a time to live on Olympus. DC Rebirth, Omen was Featured in Titans Hunt and in the Rebirth Titans book until the new lineup with Nightwing, Donna Troy, Beast Boy, Raven, Miss Martian, and Steel.
Lilith's Titan origin story from NTT actually pre-dated Donna Troy's Trioa storyline where she became a Titan "seed" and given powers and abilities from the original Titans of Myth.
So that new Wonder Woman trailer sure does make Donna look silly