They're different tenses and mean different things.
"She teaches..." means that she does it often, but isn't necessarily doing it now.
"She is teaching..." means that she's doing it right now, but doesn't necessarily
It's possible for just one or both of the statements to be true.
They both sound natural. You just need to make sure you don't mix them up.
Here's another example:
I play squash, but I'm not playing squash because I'm sitting at my computer typing this.