Since she's been in a bad mood, the whole family has been walking on eggshells around her.

eggshells 是名词 eggshell 的复数形式，字面意思是"蛋壳"。 walking on eggshells 是一个英语习语，字面意思是"在蛋壳上行走"，比喻"小心翼翼、如履薄冰"的状态，因为蛋壳非常脆弱易碎，需要特别小心地对待。这个习语用来形容为了避免惹怒或冒犯某人而格外谨慎的行为。