It may have both the "she never sleeps" as a constant syndrome in one context and "she is not sleeping" in another, but DL never likes the gerund translation, even though I think it would be the preferable translation in many cases. Some of the acceptable translations (by DL) would nail someone as not a native English speaker.
Mi madre, quien es mas viaja, definitivamente no dureme mucho en la noches, menos ella toma pastillas para dormir. Eso se determinado a traves de pruebas.de suenas. Es una problema para ella. "Is not sleeping" no es tan bueno.
"My mother, who is older, definitely does not sleep much at night, unless she takes sleeping pills. That has been determined through sleep tests. It's a problem for her." "is not sleeping" doesn't work as well in this context.
Not in general. It looks "definitivamente" means both "definite" and "definitive". http://www.spanishdict.com/translate/definitivamente and http://www.linguee.com/english-spanish/search?source=auto&query=definitivamente
But in this sentence, I don't think definitively makes sense.