My small 3 kg cat licked some cardamom-spiced sauce — is her size a bigger concern?

No, her small size doesn't make this more dangerous. Cardamom is safe for cats in the tiny amounts used for cooking and seasoning. The trace quantity she likely ingested from a sauce is not a toxicity risk. You might see some mild digestive grumbling simply because it's a new flavor, but that's not due to the spice itself being harmful. Just ensure she has water available and her usual routine isn't disrupted.