I don't really have too much to add here, but I have flown over 391 flights with Iberia, at least half of those to non-Spanish-speaking destinations, and I have never encountered a member of the cabin crew who doesn't speak English.

In all honesty and without trying to be disrespectful, I think there are big gaps in the situation here that you should try to figure out with your partner.
> "Apparently, she was just pointed to water or soft drinks and nothing else."
- Apparently, it doesn't really result in reassuring; if by some sort of miscommunication and/or potentially making gestures, the crew could have understood that she only wanted water altogether.
> "Upon hearing this, I immediately contacted one of the crew to find out what happened.. and then they gave her an entree."
- This just proves my point above. But you don't share what they told you about "what happened".
> "The rest of the flight, every-time my parter asked something she was answered back in spanish and moved on."
- This could be due to how the point above was handled if they offered her something and she only chose water and potentially not wanting anything else, to then have someone go after them to why the person was not served what was supposed to get. So without understanding the full picture... it's good to assume that this all was a clear miscommunication case and most likely the FAs having a rough day.