As someone who climaxed during a sexual assault, I can tell you that wetness is the bodies automatic response to stimulation. The pussy lubricates to ease penetration. Period.

Further, juicing up isn't the only or most reliable indicator of arousal, especially as women of a certain age have a harder time producing natural lubrication and their lack of wetness doesn't mean they aren't having a good time. Nipple erectness, eye dilation, pulse and perspiration can be even more useful to determine how well your female is enjoying what is occurring. Further, just because her body is reacting, doesn't mean that her mind is there too. Verbal reassurances are still the best way to indicate her enjoyment.