The Snake Wife

Suggestions:

Legend of the Shadowy Ninja: The Ninja Dragon Phoenix the Ninja Ninja Masters 4: The Possession Ninja Evil Strike The Monster Kills in the Mansion of Terror

Kwan discovers her husband is married to another woman plus has a child with her. In retaliation she becomes romantically involved with a deadly snake (we don't know quite how that works since we haven't seen this) and a series of serpent deaths soon follow.