[aMorePerfectUnion]

“So, is she going to leave her second “husband” and renounce her fornicating ways?”

If divorce (for adultery) and death didn’t end a marriage, God would not have allowed remarriage... and Christ would not have reaffirmed God the Father’s words.

If she did not divorce over adultery - or if her first husband isn’t dead, she has deeper issues to repent from.

[Mrs. Don-o]

The Catholic Church doesn't recognize divorce/remarriage in cases of adultery. Annulment (a finding of nullity) can be obtained only if the first marriage was actually for some reason invalid right from the start. For instance if one of the spouses never actually intended a lifelong, faithful, monogamous union.

[Campion]

Everyone here agrees that someone can remarry if their spouse dies.

Divorce was permitted in the Old Testament for any reason. However, the penalty for adultery (by a wife, not by a husband) was death.

Christ also did not permit divorce for adultery. The passage in Matthew misinterpreted to mean that does not use the Greek word for "adultery", but a different word, porneia (often translated "lewdness"). The implication is that people who are unlawfully married (due to consanguinity, for example) or simply "shacking up" are free to contract a real marriage.

Telling people they can get divorced and remarry if they commit adultery simply tempts them to commit a serious sin to get what they want, something Our Lord was not in the business of doing.