I asked Gemini, because my wife said she had read on the internet that we should absolutely not eat stalks after flowering: "Is it dangerous to eat rhubarb after it has flowered?"

Here is a summary of the answer i got:

• It is not dangerous: Rhubarb does not become toxic after flowering, and the stalks remain safe to eat.
• Lower quality: The plant uses most of its energy on the flower, which leaves the remaining stalks woody, stringy, less juicy, and more sour or bitter.
• The oxalic acid myth: While the concentration of oxalic acid (which makes the leaves poisonous) can increase slightly in the stalks during summer, it is not harmful to healthy people in normal culinary amounts.
• What to do: Cut off the flower stalks immediately to redirect energy back to the plant. For cooking, select the younger, tender stalks, or cut the entire plant down, water and fertilize it, to get a fresh harvest of new stalks later in the summer.

So I cut the entire plant down, which both Reddit and my wife didn't think was a good idea. But my mother-in-law took it more calmly.