I can't think of any scenario where Marylin's answer makes sense.
a) If the humidity is high, the fan won't help, but then the
person won't get dehydrated, contrary to what she said.
b) If the humidity is not high, the fan helps quite a bit,
contrary to what she said. This is why people buy fans.
The amount you have to drink to keep hydrated under the
stated conditions, sitting on the porch, is not zero but
not unreasonable.
*) Maybe there is some other scenario in which what she said
makes sense, in which case her answer is only "mostly" wrong
... but I can't think of any such scenario. More importantly,
in any case, she should have /told/ us what she is talking
about. We shouldn't have to guess.
I just got through riding my bike for 30 miles. It's 105
in the shade and there's no shade. Also no breeze. On the
other hand, the humidity is 20%, so it's not hard to keep
cool, given enough to drink. My point here is that I'm a
lot cooler when I'm in motion than when I stop. A fan (or
a breeze) helps enormously under these conditions.