The key in the Civil Code is Art. 195 (injuries to “body, health, reputation, liberty, credit, privacy or chastity of another, or to another’s personality in a severe way”). In the Criminal Code, “Offenses Against Freedom” start at Art. 296, and “Offenses Against Reputation and Credit” start at 309.
For the amount that should be claimed, the extent and strength of evidence needed, and things in general, your friend should probably talk to a lawyer, but if he/she enjoys reading legalese, there’s always 裁判書查詢 at jirs.judicial.gov.tw for (non-binding) precedents and insight into the minds of Taiwan’s judges.