Yes, as Jimmy points out, the enzymatic activity is affected by temperature and a longer mash time would be appropriate for a lower temperature mash.
I do have to wonder about the effect of mashing at such a low temperature though. That would be taking a lot of body and head potential out of the wort. While I am a proponent of mashing to get fairly high fermentability, I'm concerned that this approach might be too much. Conversely, too many brewers mash at too high a temperature and the fermentability suffers and body is excessive.
I'm curious why she prefers to mash this low? I prefer the low end of the alpha amylase activity.