。
She is soft on her child.
Literal
She [topic-は] her own child [toward-に] sweet/lenient is.
甘い ('sweet') in this idiomatic ~に甘い construction means 'soft on, lenient toward, indulgent of' — its sweet-tasting sense extended to a sweet-but-overly-permissive disposition. Common in discussions of parenting, romantic partners, and supervisors who don't enforce rules. The opposite is ~に厳しい ('strict toward'). 子ども (with kana for ども) is a slightly softer, more child-friendly spelling than 子供 — the same word, but lighter in feel.