Bad advice is bad.
The whole "Learn Mandarin" thing is just silly. This really came about ten or so years ago when the Chinese economy was surging, and there was speculation that there would be opportunities as China moved into the second spot. Since then, a regime change hasn't really opened up anything and their economy has started to sputter. Given that, there is no suggestion that Mandarin is threatening to become the international business language, and attempting to learn a language there is little chance of using is a waste. (Of course, if she's interested in learning the language on its own merit, that's something entirely different and of value.)
Conversely, learning Spanish still has immense value considering the large immigrant population in the United States.