Less so than one whose day job is a terrorist?
The phrasing of this question confuses me so I don't know what you are asking.
I maintain that if Marlene is left without a supervisor in the remake after they leave the bar, then Barret will look worse for it as a father. It will also appear inconsistent with how much Barret cares for Marlene in the rest of the story. I can shrug this detail off in the original game as a humorous observation due to the cartoon-y presentation, but I just can't see it working in the remake.
We'll just have to agree to disagree.
Except in the game, Barret already calls himself out on it when he talks to Elmyra, and its a very serious moment. He knows he should be at Marlene's side, but his quest for vengeance is so ingrained in who he is, he can't ignore it, and it pretty much rips him apart on the inside. It's an overt character flaw that makes him who he is.
Life in Midgar Slums however, reminds me of Detroit more than any other place. I've lived there, albeit only for a short period of time, but I can say that the people of those sort of neighborhoods keep a close eye on each other. My father lived there for much longer than me, and explained to me how at one point his car had been jacked. Practically half the neighborhood turned up on his doorstep at 6 in the morning to check on him, and make sure he was okay.
People have this dramatic idea that low income, or even destitute places, be the slums, trailer parks, or even shanty towns, are these harsh lawless places where nobody is ever safe. Its true, there are desperate people; My bike was ripped off it's chain by some asshole in the middle of the night. But for the most part, they become more like small villages. Everyone looks after each other. Sector 7 seems to have very few people living there, and they all have likely known each other for decades; Just look at all the people who came out to bid Johnny farewell.
I'm pretty sure they all know who Marlene is, and would make sure nobody, or any monsters would bring her to harm. Not to mention they also probably know that Barret, Tifa, and the rest of Avalanche would rip them in half if anyone DID try to hurt her. As for Marlene just being on her own, she's likely had to mature quickly, and understands not to do anything overtly stupid. I do think it'd make a little more sense to age her up to 6/7 though. Even in AC, she seemed more based on 9-10 year old.
In my mind, Marlene is just left to her own devices, and everyone who lives there knows not to go into the unattended bar owned by a woman who can punch through metal, and frequented by a 7 ft tall man with a gun on his arm, who could probably benchpress a car. Marlene is just "Holding down the fortress" as adults like to say to kids when they have no choice but to leave them alone for a while.