English is not their native language. Acceptable use patterns may be different in the Netherlands.
Edit: besides, the Dutch (especially younger ones) tend to speak English at practically native speaker level. The cited example may even be an example of that: if you can sound dumb in the same way that a native speaker would, your English is obviously very good :)
She was probably just nervous and didn't know what to say. So she said the first thing that came to mind...
Don't overestimate us. Dutch people tend to be able to communicate in more languages than their own and be prepared to do so when encountering foreigners, but fluency in English is not widespread.