I am a bit on the fence but looking at the bigger picture I wondered the same AQoA about the father.
Although realistically how much longer does this go on for? They have had 6 children removed - which will be for good reasons. It isn't fair to expect children to continue to go through that.
I think in an extreme case like this (at least I hope it is considered extreme) it sits better with me that the parents are sterilized than more kids be born with inadequate care and having to be removed from home.
None of which changes the fact that she most likely won't survive another one.
The entire situation is terribly sad.