Does it matter: what kind of pool it is? Yesish, something about the pool is relevant.
where the chairs are located relative to water? No.
to any structure? YES.
Was it a real rain? Yes.
or just mist? or spray? or drizzle? The intensity is irr, but it is real rain.
Does she want to cause rain? Yes.
Does she do a rain dance? No.
Does she do something scientific? Only in the sense that it is a logical step to produce a desired result.
Unscientific? Not really.
Does Andrea make an announcement (e.g. over intercom) that it's going to rain? No.
So that people who are still there remove their towels, and all towels that are still on the pool chairs are assumed to have been left behind and can then be removed by staff? This is the effect, but there is no announcement, just rain.
Does Andrea carry out cloud seeding? No.
Does she have a super power? No.
Is she Storm? Nah, if I could have used the name Ororo Munroe I definitely would have.