Siri says: [Contact] "is not on your Find My list"

I just tried asking Siri "Hey Siri where is my mom?" and it replied she's not on my Find My list. This is not true because if I manually go to the Find My app, tab People, there she is. If I tap on her name, the app can even show me her contact card, but Siri keeps saying she isn't there.

I have another friend in that Find My list other than my mother, if I ask Siri to find that friend's location, Siri can instantly show exactly what I want, but why can't Siri do the same to my mom? Are there some settings I missed? Or settings on my mom's end?

I tried both contacts, on my iPhone 6s+ and iPad Gen 6, same results, even after restarting all devices. I do have my mom's iCloud email in her contact list.