Slavic languages are all quite similar in many aspects, so if you're a native speaker of one and you're exposed to another over a longer period, you can pick up a lot. I've learned to understand Russian exclusively through music, for example.
It's obvious she never learned the language formally as it sounds like a strange mixture of Serbian and Croatian, but she's quite fluent indeed.
As for Anja Spasojević, she's a true gem! She absolutely needs to work in the media! I'm sure she'd help put women's volleyball on the map in Serbia even more.
She gave this interview before the start of the second phase, so she summarized Serbian performance in the preliminary pool and she's very impressed with how composed they are and how well they're playing. However, she also warned that the USA played extremely badly in that match and that it's not a realistic account of their abilities, so if we get to play again, we can expect a totally different American team. Still, she's confident we can beat them no matter what if we play our game.
Then she talked about the opponents in the second stage:
Poland - if you let them play their game, you're screwed, so you have to impose yourself right from the start. They are a good team and they have the crowd behind them, but objectively speaking Serbia is better and should win the match in straight sets. But it's important to get into the game right from the start.
Dominican Republic - they're like Serbia a long time ago. A quality team that lacks consistency. They have great attackers and Brenda Castillo is an amazing libero ("I actually remember her! She played in my time! I don't know how the hell she manages to keep going, but she does it and she does it so well!") and they can play on an extremely high level for a while, but they can't keep it up. Sooner or later they're going to drop down so it's important to be patient and wait for your chance if you get into trouble against them. Serbia might lose a set to them, but should win.
Thailand - "a traditionally difficult opponent", playing the Asian style that never suited us. They're fast and play amazing defence, so it's important to keep focus and don't give away points. If we play like we can, we should win comfortably.
Turkey - turns out she's a big fan and always roots for them unless they're playing against Serbia. That's mostly because she's very close friends with Eda. According to her, the MBs are very good, the setter is good, the OPP (Ebrar) is unreliable because you never know how she's going to play, she can be either amazing or awful. The OHs are the weakest link. But they also have Guidetti's system behind them and they keep fighting until the very end and in her opinion they're the most difficult opponent in this phase.
Generally, she's very happy with the way the team is performing and she thinks Santarelli established a very good connection with the girls. She believes Serbia can go all the way if they keep playing like they can, but also says you can never discount the possibility of having a bad day when nothing goes right for your team, like she believed it happened to USA against Serbia, and she hopes we can avoid them.