It's very much Fridge Squick when you remember that she, like her brother, is only twelve.
Also, the fact that the ending seemed a little Narmy until you realize that what good Lex had said earlier was true: though the remainder of the Crime Syndicate probably could have taken down the Marines, Ultraman realized that now the people of his Earth were no longer afraid of him, and that fighting the Marines would have been futile: not only would they had to have faced the full Justice League again, but they would have to face everybody on their Earth who was willing to fight back, and that it was a pointless battle.
Here's one that only makes sense if you take the DCAU into account. Flash is repeatedly shown to be the most moral of the League, and the League would fall apart without him. His counterpart Johnny Quick is the only one of the Crime Syndicate with some good in him, and the Syndicate is defeated almost immediately after he dies.
Power Ring doesn't seem to care about whether the mob succeeds or not - makes sense, since he's still a space cop.
The movie was originally supposed to be made between Justice League and Justice League Unlimited. The new JL Watchtower with transporters, Wonder Woman's invisible plane and the membership drive bear this out. The only thing keeping it from actually fitting in regular continuity is Hal Jordan as Green Lantern. The fact that However, because its about parallel Earths, with some only bearing the smallest differences, this story could have still happened in the regular Timmverse with John Stewart as the Green Lantern instead of Hal.
There is one more thing that keeps it from fitting in the regular Timmverse (the quick flashes of the End of Mars does not fit with what was established in Justice League's introductory episode), but otherwise accurate.
The difference in the Mars flashbacks is merely stylistic if you take into account that the invaders in the pilot of Justice League were based on the White Martians, who are the ones shown in the flashback.
There's also the fact that regular-Earth Lex Luthor is in a prison cell, while at that point in the DCAU, he was running for president. (Why am I the only one who's noticed that?)
You have to wonder what Black Canary would have thought of Wonder Woman urging J'onn to remain on Earth-2 to be with Rose. Probably approval, since she did the same thing to be with Green Arrow.
Meta brilliance: The first few Crime Syndicate figures released in the Justice League Unlimited toyline were Ultraman, Power Ring and Superwoman. They are the Crime Syndicate survivors, so even the DCAU-based toyline kinda fits with the movie.
When Owlman realizes that his choices are pointless, he's more correct than he thinks. According to Word of God, it's impossible to destroy Earth-Prime because once sapient life arrives, divergence will ensue for every choice made just like on any other world. In short, Owlman would have destroyed one of Earth-Prime's offshoots. Neither he nor any copy of him will be able to even touch Earth-Prime.
The designs of Ultraman and Johnny Quick are noticeably different from any of their comic book counterparts, particulary the abundance of colour yellow. However, this starts to make sense if one remebers that a green power ring is weak against yellow - it isn't just a fashion choice, it's a precaution against Power Ring, who seems to have problems with authority.
This may be negated by assuming origin stories for characters from the comics, but based purely on the total lack of backstories for Crime Syndicate members in the movie, one might assume Power Ring to be a member of the Green Lantern Corps. If that were indeed the case, it would mean his ring had chosen a villain... which would, by extension, mean the Guardians of the Universe and the entire Corps must also be villains.
More then likely he is like the comic version, using an Alan Scott style power ring that is similar but seperate to the actual Corps rings
In the comics the Crime Syndicate come from the Anti-Matter universe, and there are no Guardians of the Universe / Oa. Instead, there are the Weaponers of Qward, enemies of the Guardians and the ones who gave Sinestro (ie. the mainstream Sinestro) his yellow power ring. The Anti-Matter universe and all universes were created thanks to the actions of the renegade Guardian / Oan Krona, due to him messing around with time-travel and the Big Bang. I'm not entirely sure if the Guardians even have counterparts, evil or otherwise, in any universe, but the do not have them the Anti-Matter universe. The Weaponers of Qward are a distinct species and look and act completely different, though I believe Qward occupies the same space relative to Oa in the Anti-Matter verse.
Alternatively, Power Ring is in a situation similar to pre-yellow ring Sinestro: he's abusing his power, but keeping it secret from the Corps.
When Owlman merely says "It doesn't matter" as he is destroyed, It sounded less like begrudging acceptance of his death, but realization that he's not done yet. He says earlier that there are "alternate versions of him." If alternate universes are created by every choice, big and small, there are still omnicidal owlmen out there. How long until one gets the means to carry out the same plan?
It doesn't matter what he does, Earth-Prime will still exist. If he blew up Earth-Prime, he would have only created two new Earths (one fine, one exploded) while Earth-Prime still exists untouched.
When the Justice League needs to devise an alternate method to follow Owlman to Earth-Prime, Johnny Quick volunteers to help save the multiverse. But it wasn't just Batman who knew the fatal outcome. Luthor is every bit Batman's equal in intellect; How could he not know the volunteer would die? He says the person for the job has to be fast, as if he didn't know they had TWO super speedsters in the group. Rather than outright ask the Flash who would not have hesitated, he set Batman up to rebuke him so Johnny would take his place. The horror is that both Batman AND Luthor are ruthless enough to manipulate a villain to make a sacrifice if it will spare one of their own. And they even did it simply by playing off of each other.
If Owlman's beliefs about how the multiverse works are correct, then there could be a world where the Justice League refused to help stop the Crime Syndicate.