Why is my daughter asked to enter my AppleID password to open *any* app on her iPhone?

Question

Preamble:
When iOS 8 dropped and my family of 5 had all upgraded, I set up Family Sharing. As it turns out, it's an incomplete solution and is therefore completely useless for isolating the spendy account (home sharing, iTunes share, etc.), but setting all that aside, I figured we might give it a shot.
It's OK - it's annoying that my kids need permission to download free apps, but OK. However, there is this strange bug I can't explain of figure out how to fix.
Problem description:
My daughter is logged into the iTunes store with her own AppleID and all looks well. However, any time she attempts to open any app at all other than the builtin apps, she gets a popup asking for the password for my AppleID! ***? Why is my AppleID even a thing on her phone?
Post-description rant:
Perhaps I was foolish to switch this on so soon - or indeed at all; I still have inexplicable inabilities to play a huge number of tracks in iTunes Share, across all devices (though it is not the same set of tracks on each device). But on the other hand, I don't see this issue described when I google around, so perhaps this is an anomaly, maybe some inconsistent/corrupt data, and there's a standard set of "switch it off and on again" steps that people might be able to suggest to take care of it.

Answer 1

j0ni wrote:
Preamble:
When iOS 8 dropped and my family of 5 had all upgraded, I set up Family Sharing. As it turns out, it's an incomplete solution and is therefore completely useless for isolating the spendy account (home sharing, iTunes share, etc.), but setting all that aside, I figured we might give it a shot.
It's OK - it's annoying that my kids need permission to download free apps, but OK. However, there is this strange bug I can't explain of figure out how to fix.
Problem description:
My daughter is logged into the iTunes store with her own AppleID and all looks well. However, any time she attempts to open any app at all other than the builtin apps, she gets a popup asking for the password for my AppleID! ***? Why is my AppleID even a thing on her phone?
Post-description rant:
Perhaps I was foolish to switch this on so soon - or indeed at all; I still have inexplicable inabilities to play a huge number of tracks in iTunes Share, across all devices (though it is not the same set of tracks on each device). But on the other hand, I don't see this issue described when I google around, so perhaps this is an anomaly, maybe some inconsistent/corrupt data, and there's a standard set of "switch it off and on again" steps that people might be able to suggest to take care of it.
Wherever I said "iTunes share" I really meant iTunes Match. Sigh.