Your father is angry with me because he thinks I almost got myself killed,' said Sabriel, with a slight grin. 'I don't understand it myself, since I think he should be glad that I didn't.
Sabriel explains to Lirael that her father is upset with her because he believes she almost got herself killed. He is angry despite her survival, which she finds confusing because she thought he would be glad she is safe.
She remarks humorously that she doesn't understand her father's reaction, as she personally believes he should be happy she survived rather than upset about her near-dangerous experience. The quote highlights her confusion and possibly her own attitude towards danger and parental concern.