@Xenograg
I mean...
"She rolled very low, and in turn, I told her that there were no traps she could detect."
She knew she rolled low, you said no traps "she could detect".
Rules as written the player knew the character wasn't sure, and opened it anyway.
At my table she takes the poison.
Because she could have decided to not open it, or asked another player with decent Investigation to give it a 2nd look with a higher DC.
I take it easy on my players but that is why we do dice rolls.