、。
If I tell my mother, she'll worry — so I won't say anything.
Literal
Mother [to-に] say-[if-と] worry [because-するから], this thing [topic-は] say-[will-not-まい].
~まい is the negative volitional — 'I shall not, I will not.' It's the literary/formal version of ~ないようにしよう. 言うと心配する uses the natural-consequence conditional と: 'if I tell her, she'll worry (as a natural result).' から marks the reason. The speaker's protective impulse is conveyed through this single decision sentence.