The moment she held the baby, a sense of motherhood awakened in her.
That novel takes motherhood as a major theme.
The moment she held the baby, her maternal instinct awoke.
I feel a maternal warmth from her.
She has a strong maternal instinct and is kind even to animals.
母性 is an abstract quality (motherhood/maternal instinct), whereas 母親 is the concrete noun for a mother as a person.
A Sino-Japanese compound written with 母, 'mother,' and 性, 'nature' or 'quality'; the spelling transparently represents the idea of maternal nature or motherhood.