That's actually a pretty good theory, and it honestly works in the context that we know of.

In general I really do like particular fanon theories, and there are a lot of them out there, because most of them do work, especially considering that there's been a huge lack of background information to the actual lore of angels within the show itself (and some ends up just getting forgotten or made up on the spot, but that's another rant altogether.) So with your theory it really does work in context of what was revealed in canon. Some angels don't like humanity, some believe that humanity corrupts the very nature of angels. For example, we're seeing this right now with everything happening with Castiel. So it's not improbable that with Anna, after willingly ripping out her Grace and wanting to become a human, Heaven viewed her as a disgrace and an abomination.

And just yeah. Fan theories I like, because it allows us to make sense of the fuckery that is canon. ;)