This is a very old controversy: is it always better to have a native speaker as a teacher or language coach? Short answer: Not always. What you are avoiding in any case are the mistakes or potential pitfalls that a non-native speaker might have. However, their being native speakers is no guarantee of their qualifications, just as most spanish speakers would not be qualified to teach Spanish to anybody.
There are many qualified, excellent native teachers, of course. And maybe your goal is not to talk like the BBC or the CNN. So it also depends on your goals. Besides, really good native teachers are in high demand and charge a lot, therefore your budget may also compromise your range of options. Depending on the skills you would like to work on, maybe you do not need a native speaker.
Just as you and I are not perfect Spanish speakers and we make mistakes, native speakers also make them. Watch below a youtube video which explains some of those mistakes. We are talking about correctness in terms of grammar and standard, educated pronunciation. You may be thinking right now… what if I do not want to speak correctly, like the BBC or the CNN anchors? What if I want to speak like Eminem? Or like the Kardhashians? No problem with that.
So, not all native speakers – of any language – are qualified to teach other people their language. They may speak it, they may even write it well, but they do not necessarily understand how it works internally, which comes very handy when you are teaching your students and they ask you questions.
The lesson to be learnt here is very simple: choose your teacher wisely. In order to do that, define your goals and reflect on your motivations. Once you know what your goals are and if you are truly motivated, then start looking for your ideal teacher. Native speaker or otherwise.