So she doesn't speak English well and her main language is Spanish. You spoke the phrase in Finnish and there is one word that may slightly sounds like a naughty word. However your entire phrase was in a language different than hers. So is she such an idiot that she thought the entire phrase was in Spanish? Or did she think you were just throwing out random foreign words and one happened to sort of sound like a bad one she knew of. Is she slow or something? The perceived word and context of the phrase don't really mesh well in Spanish. So the first scenario is that the person is a total fucking moron and doesn't even know her native tongue very well.
It does sound as though there are at least two languages being spoken at your work so miscommunication seems like it could happen regularly. Seems HR should understand this. However, none of them tried to get clarification on what you said and didn't want to listen to you when you tried to explain. There was no effort on their part to understand, unless that was the actual ploy. It sounds like she heard only what they wanted to hear and used that to cry to HR.
Honestly, this feels more like harassment. Either total stupidity or harassment.