Hi

Just make sure she has worked as a nanny before,

the language barrier is not a major problem

they are very quick learner and before you know she will understand everything you say.

check, how old she is, if she is between 23 to 30 years and had previous experience then you will be fine.

The rest is just all your luck, you can bring someone who understand your language very well & has previous experience but still isn't good at work.

Good Luck