Is it permissible to divorce one's wife if her betrayal is proven by pornographic WhatsApp conversations with a friend, especially since she exploited her husband's illness, and confessed to her actions?

If the wife has committed what was mentioned, then she has committed a clear evil and a manifest sin. Do not rush to divorce her; instead, advise her and call her to repentance. If she repents and becomes righteous, then keep her, treat her well, strive to keep her chaste, and raise her upon goodness. If she does not show repentance and righteousness, then separation from her is recommended.