Answer:
In this context, to be mortified means to be embarrassed, to be humiliated.
Explanation:
We can analyze the meaning by studying the word of origin: mortificare. If, like it says in the given statement, mortificare in Latin means to cause death, we can infer how Janis felt, after she realized her brother had read her diary. She felt so embarrassed and humiliated that she probably felt like dying, in a figurative way. She was so mortified, she felt she was dying.
