Consider inviting all neighbors except her over (bonus if it’s while she’s doing this) and while you are enjoying the afternoon give a small “tour of the yard” and as a group look /point at her pool and explain the water thing and frequency. Be friendly about it and loud.

Maybe your friends can suggest ways to correct this.

Hopefully it will draw her out and a friendly group conversation can take place.

1-she will note she wasn’t invited 2-she may be shamed enough that her other neighbors are suggesting solutions peer pressure may get her fanny in gear.

Are you the only neighbor who gets to enjoy this rude neighbor?

Might be worth looking at the municipal rules and if illegal you can call the city and report them.

Pumps are about $100.00 and the hose can be long enough so it goes into a storm drain on the street so I suspect she’s lazy.

(Wikipedia -To drain your pool without annoying your neighbor, use a submersible pump with a hose to direct water to a storm drain in the street or a sewer cleanout on your property. For a faster method, use a pump to push the water out; for a slower method, siphon it by filling a hose with water and letting gravity do the work, ensuring the outlet end is lower than the pool. Crucially, check with your local municipality for any specific rules or restrictions on pool draining before you begin. )

Video tape the pool draining into your yard. No faces or address info.

Make a voiceover and message “don’t be like this neighbor, 6 times a year we have to deal with the water coming into our property and the pool owners can’t come up with a solution.”