Carolyne - with all due respect, if you're going to quote then quote the whole thing not just what serves you.

"From her description, it felt like they were not really divorced but in an open relationship in many aspects that made me question this toxic triangle where my neighbor looked more like a backup than the main partner. "

And here the keyword is "it felt" - that's not the same with being a fact. The fact was they were divorced, but it felt like they were in an open relationship.

Clearer now?