Demasiado + another adverb

Demasiado + another adverb
 

Is it correct to use another adverb after 'demasiado'?
Example:
Mi amiga habla demasiado rápidamente.

I have heard some natives say:
Mi amiga habla demasiado rápido.

Many thanks.

There is nothing wrong with demasiado rapidamente except I don't think anyone uses it. In this case, your friend is right.

Here's a good explanation.

Many thanks, guys.