I mean part of the problem here is SE playing with time travel, because Venat made the choices she did based on what we told her in addition to the actual real proof that what we said is true when the world, you know, started to actually end just like we said and just like Meteion told her, too. Which means I still have no idea what would've led her to make those choices if she hadn't met us, but it seems like they're implying (or at least it kinda makes sense) that she would've sundered the world anyway even without the bit of foreknowledge we gave her by traveling to the past.
Interestingly it isn't actually explicitly stated that Venat did keep that foreknowledge to herself. She explicitly states that she "must carefully consider who can be trusted and bring them into the fold." She kept it from the Fourteen to avoid tipping off Hermes... and if she told them immediately, then they would need to come up with a reason for suddenly taking the request to take up the seat of Fandaniel back if it came to it (and deprive themselves of any help he could offer in the 'present' time), or else risk Hermes potentially actively working against them. Presumably that means she did intend to share it with someone, but either didn't trust Hythlodaeus or Emet enough to not tell (and in Emet's case possibly not wanting to push him to go against the 14 as a member of the 14?) or had some other reason... or did tell them but either it was too late or they still ended up unable to do anything about the Final Days.
We don't actually know exactly how much time passes between Meteion leaving Elpis and the Final Days actually starting, but it was enough for Venat to gather a (apparently very small) group of very loyal followers and, evidently, come up with more than one plan of action - one of which it sounds like was entirely different, but that as far as I remember never gets explained. Back in ShB when we first learn Venat is Hydaelyn's heart, she and the other ancients talk about how the Convocation won't listen to their petition to turn away from their "current path" (presumably the whole trading lives to Zodiark forever thing) and she says it's "plain they (the 14) will not countenance a permanent solution." Whatever that means.
There are gaps in our knowledge obviously, gaps I wish they had touched on more for sure, but I don't think I can rightfully agree with the conclusion that Venat didn't give her people a chance before jumping to the extreme actions she took, which she admitted were extreme, and acknowledged directly led to a whole lot of suffering.
Bit of a tangent maybe, but I'm actually interested to see if Pandaemonium wraps up any of the loose ends here. We still don't know what Azem was doing during the End Days, or why they didn't even answer Venat & co's call for help. We also don't know how Emet & co. dodged the sundering. The main story is over, but there are definitely still some open questions roaming around, and we aren't through with Elpis yet.