"Why did you marry again, mamma? It would have been nicer if you had not."
Mrs. Davilow coloured deeply, a slight convulsive movement passed over her face, and straightway shutting up the memorials she said, with a violence quite unusual in her—
"You have no feeling, child!"
Gwendolen, who was fond of her mamma, felt hurt and ashamed, and had never since dared to ask a question about her father. (3.5-8)
Gwendolen doesn't learn this until later, but sometimes people marry for reasons other than love. We get the vibe that Mrs. Davilow didn't really want to marry her second husband, but may have done so to help Gwendolen.