Also: If somebody is romancing two girls and those girls are romancing each other then it's just polyam.
Eh… only if they each now and agree to it. Polyamory is when you are in a relationship with one or more person that may themselves be in a relationship with one or more other person, but they each have to now about the other partners have their say on which to include or not. Otherwise it’s just libertinism/open‑relationship.