This was posted on this site back in 2016, so I don't know if this will help or not.
https://forums.thesims.com/en_US/discussion/901375/gurl-stop-casting-this-spell
But if you go down to @igazor comment they mentioned this.
I thought this could be reached with NRaas Retuner, but apparently it's too complicated for that. But if not averse to using mods, you want bluegenjutsu's No Autonomous Cast Sunlight Spell mod. She has a separate one for each type of spell, in case that becomes an issue. They are at The Sims Asylum (google for link), look for bluegen's section under developers then Occult Mods. Free registration at The Asylum is required to see anything there.
